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Annotation of 43BSD/usr.lib/sendmail/doc/rfc822.lpr, revision 1.1

1.1     ! root        1: 
        !             2:  
        !             3: 
        !             4: 
        !             5: 
        !             6: 
        !             7:      RFC #  822
        !             8: 
        !             9:      Obsoletes:  RFC #733  (NIC #41952)
        !            10: 
        !            11: 
        !            12: 
        !            13: 
        !            14: 
        !            15: 
        !            16: 
        !            17: 
        !            18: 
        !            19: 
        !            20: 
        !            21: 
        !            22:                         STANDARD FOR THE FORMAT OF
        !            23: 
        !            24:                         ARPA INTERNET TEXT MESSAGES
        !            25: 
        !            26: 
        !            27: 
        !            28: 
        !            29: 
        !            30: 
        !            31:                               August 13, 1982
        !            32: 
        !            33: 
        !            34: 
        !            35: 
        !            36: 
        !            37: 
        !            38:                                 Revised by
        !            39: 
        !            40:                              David H. Crocker
        !            41: 
        !            42: 
        !            43:                       Dept. of Electrical Engineering
        !            44:                  University of Delaware, Newark, DE  19711
        !            45:                       Network:  DCrocker @ UDel-Relay
        !            46: 
        !            47: 
        !            48: 
        !            49: 
        !            50: 
        !            51: 
        !            52: 
        !            53: 
        !            54: 
        !            55: 
        !            56: 
        !            57: 
        !            58: 
        !            59: 
        !            60:  
        !            61:      Standard for ARPA Internet Text Messages
        !            62: 
        !            63: 
        !            64:                              TABLE OF CONTENTS
        !            65: 
        !            66: 
        !            67:      PREFACE ....................................................   ii
        !            68: 
        !            69:      1.  INTRODUCTION ...........................................    1
        !            70: 
        !            71:          1.1.  Scope ............................................    1
        !            72:          1.2.  Communication Framework ..........................    2
        !            73: 
        !            74:      2.  NOTATIONAL CONVENTIONS .................................    3
        !            75: 
        !            76:      3.  LEXICAL ANALYSIS OF MESSAGES ...........................    5
        !            77: 
        !            78:          3.1.  General Description ..............................    5
        !            79:          3.2.  Header Field Definitions .........................    9
        !            80:          3.3.  Lexical Tokens ...................................   10
        !            81:          3.4.  Clarifications ...................................   11
        !            82: 
        !            83:      4.  MESSAGE SPECIFICATION ..................................   17
        !            84: 
        !            85:          4.1.  Syntax ...........................................   17
        !            86:          4.2.  Forwarding .......................................   19
        !            87:          4.3.  Trace Fields .....................................   20
        !            88:          4.4.  Originator Fields ................................   21
        !            89:          4.5.  Receiver Fields ..................................   23
        !            90:          4.6.  Reference Fields .................................   23
        !            91:          4.7.  Other Fields .....................................   24
        !            92: 
        !            93:      5.  DATE AND TIME SPECIFICATION ............................   26
        !            94: 
        !            95:          5.1.  Syntax ...........................................   26
        !            96:          5.2.  Semantics ........................................   26
        !            97: 
        !            98:      6.  ADDRESS SPECIFICATION ..................................   27
        !            99: 
        !           100:          6.1.  Syntax ...........................................   27
        !           101:          6.2.  Semantics ........................................   27
        !           102:          6.3.  Reserved Address .................................   33
        !           103: 
        !           104:      7.  BIBLIOGRAPHY ...........................................   34
        !           105: 
        !           106: 
        !           107:                              APPENDIX
        !           108: 
        !           109:      A.  EXAMPLES ...............................................   36
        !           110:      B.  SIMPLE FIELD PARSING ...................................   40
        !           111:      C.  DIFFERENCES FROM RFC #733 ..............................   41
        !           112:      D.  ALPHABETICAL LISTING OF SYNTAX RULES ...................   44
        !           113: 
        !           114: 
        !           115:      August 13, 1982               - i -                      RFC #822
        !           116: 
        !           117: 
        !           118: 
        !           119:  
        !           120:      Standard for ARPA Internet Text Messages
        !           121: 
        !           122: 
        !           123:                                   PREFACE
        !           124: 
        !           125: 
        !           126:           By 1977, the Arpanet employed several informal standards for
        !           127:      the  text  messages (mail) sent among its host computers.  It was
        !           128:      felt necessary to codify these practices and  provide  for  those
        !           129:      features  that  seemed  imminent.   The result of that effort was
        !           130:      Request for Comments (RFC) #733, "Standard for the Format of ARPA
        !           131:      Network Text Message", by Crocker, Vittal, Pogran, and Henderson.
        !           132:      The specification attempted to avoid major  changes  in  existing
        !           133:      software, while permitting several new features.
        !           134: 
        !           135:           This document revises the specifications  in  RFC  #733,  in
        !           136:      order  to  serve  the  needs  of the larger and more complex ARPA
        !           137:      Internet.  Some of RFC #733's features failed  to  gain  adequate
        !           138:      acceptance.   In  order to simplify the standard and the software
        !           139:      that follows it, these features have been removed.   A  different
        !           140:      addressing  scheme  is  used, to handle the case of inter-network
        !           141:      mail; and the concept of re-transmission has been introduced.
        !           142: 
        !           143:           This specification is intended for use in the ARPA Internet.
        !           144:      However, an attempt has been made to free it of any dependence on
        !           145:      that environment, so that it can be applied to other network text
        !           146:      message systems.
        !           147: 
        !           148:           The specification of RFC #733 took place over the course  of
        !           149:      one  year, using the ARPANET mail environment, itself, to provide
        !           150:      an on-going forum for discussing the capabilities to be included.
        !           151:      More  than  twenty individuals, from across the country, partici-
        !           152:      pated in  the  original  discussion.   The  development  of  this
        !           153:      revised specification has, similarly, utilized network mail-based
        !           154:      group discussion.  Both specification efforts  greatly  benefited
        !           155:      from the comments and ideas of the participants.
        !           156: 
        !           157:           The syntax of the standard,  in  RFC  #733,  was  originally
        !           158:      specified  in  the  Backus-Naur Form (BNF) meta-language.  Ken L.
        !           159:      Harrenstien, of SRI International, was responsible for  re-coding
        !           160:      the  BNF  into  an  augmented  BNF  that makes the representation
        !           161:      smaller and easier to understand.
        !           162: 
        !           163: 
        !           164: 
        !           165: 
        !           166: 
        !           167: 
        !           168: 
        !           169: 
        !           170: 
        !           171: 
        !           172: 
        !           173: 
        !           174:      August 13, 1982              - ii -                      RFC #822
        !           175: 
        !           176: 
        !           177:  
        !           178:      Standard for ARPA Internet Text Messages
        !           179: 
        !           180: 
        !           181:      1.  INTRODUCTION
        !           182: 
        !           183:      1.1.  SCOPE
        !           184: 
        !           185:           This standard specifies a syntax for text messages that  are
        !           186:      sent  among  computer  users, within the framework of "electronic
        !           187:      mail".  The standard supersedes  the  one  specified  in  ARPANET
        !           188:      Request  for Comments #733, "Standard for the Format of ARPA Net-
        !           189:      work Text Messages".
        !           190: 
        !           191:           In this context, messages are viewed as having  an  envelope
        !           192:      and  contents.   The  envelope  contains  whatever information is
        !           193:      needed to accomplish transmission  and  delivery.   The  contents
        !           194:      compose  the object to be delivered to the recipient.  This stan-
        !           195:      dard applies only to the format and some of the semantics of mes-
        !           196:      sage  contents.   It contains no specification of the information
        !           197:      in the envelope.
        !           198: 
        !           199:           However, some message systems may use information  from  the
        !           200:      contents  to create the envelope.  It is intended that this stan-
        !           201:      dard facilitate the acquisition of such information by programs.
        !           202: 
        !           203:           Some message systems may  store  messages  in  formats  that
        !           204:      differ  from the one specified in this standard.  This specifica-
        !           205:      tion is intended strictly as a definition of what message content
        !           206:      format is to be passed BETWEEN hosts.
        !           207: 
        !           208:      Note:  This standard is NOT intended to dictate the internal for-
        !           209:             mats  used  by sites, the specific message system features
        !           210:             that they are expected to support, or any of  the  charac-
        !           211:             teristics  of  user interface programs that create or read
        !           212:             messages.
        !           213: 
        !           214:           A distinction should be made between what the  specification
        !           215:      REQUIRES  and  what  it ALLOWS.  Messages can be made complex and
        !           216:      rich with formally-structured components of information or can be
        !           217:      kept small and simple, with a minimum of such information.  Also,
        !           218:      the standard simplifies the interpretation  of  differing  visual
        !           219:      formats  in  messages;  only  the  visual  aspect of a message is
        !           220:      affected and not the interpretation  of  information  within  it.
        !           221:      Implementors may choose to retain such visual distinctions.
        !           222: 
        !           223:           The formal definition is divided into four levels.  The bot-
        !           224:      tom level describes the meta-notation used in this document.  The
        !           225:      second level describes basic lexical analyzers that  feed  tokens
        !           226:      to  higher-level  parsers.   Next is an overall specification for
        !           227:      messages; it permits distinguishing individual fields.   Finally,
        !           228:      there is definition of the contents of several structured fields.
        !           229: 
        !           230: 
        !           231: 
        !           232:      August 13, 1982               - 1 -                      RFC #822
        !           233: 
        !           234: 
        !           235:  
        !           236:      Standard for ARPA Internet Text Messages
        !           237: 
        !           238: 
        !           239:      1.2.  COMMUNICATION FRAMEWORK
        !           240: 
        !           241:           Messages consist of lines of text.   No  special  provisions
        !           242:      are  made for encoding drawings, facsimile, speech, or structured
        !           243:      text.  No significant consideration has been given  to  questions
        !           244:      of  data  compression  or to transmission and storage efficiency,
        !           245:      and the standard tends to be free with the number  of  bits  con-
        !           246:      sumed.   For  example,  field  names  are specified as free text,
        !           247:      rather than special terse codes.
        !           248: 
        !           249:           A general "memo" framework is used.  That is, a message con-
        !           250:      sists of some information in a rigid format, followed by the main
        !           251:      part of the message, with a format that is not specified in  this
        !           252:      document.   The  syntax of several fields of the rigidly-formated
        !           253:      ("headers") section is defined in  this  specification;  some  of
        !           254:      these fields must be included in all messages.
        !           255: 
        !           256:           The syntax  that  distinguishes  between  header  fields  is
        !           257:      specified  separately  from  the  internal  syntax for particular
        !           258:      fields.  This separation is intended to allow simple  parsers  to
        !           259:      operate on the general structure of messages, without concern for
        !           260:      the detailed structure of individual header fields.   Appendix  B
        !           261:      is provided to facilitate construction of these parsers.
        !           262: 
        !           263:           In addition to the fields specified in this document, it  is
        !           264:      expected  that  other fields will gain common use.  As necessary,
        !           265:      the specifications for these "extension-fields" will be published
        !           266:      through  the same mechanism used to publish this document.  Users
        !           267:      may also  wish  to  extend  the  set  of  fields  that  they  use
        !           268:      privately.  Such "user-defined fields" are permitted.
        !           269: 
        !           270:           The framework severely constrains document tone and  appear-
        !           271:      ance and is primarily useful for most intra-organization communi-
        !           272:      cations and  well-structured   inter-organization  communication.
        !           273:      It  also  can  be used for some types of inter-process communica-
        !           274:      tion, such as simple file transfer and remote job entry.  A  more
        !           275:      robust  framework might allow for multi-font, multi-color, multi-
        !           276:      dimension encoding of information.  A  less  robust  one,  as  is
        !           277:      present  in  most  single-machine  message  systems,  would  more
        !           278:      severely constrain the ability to add fields and the decision  to
        !           279:      include specific fields.  In contrast with paper-based communica-
        !           280:      tion, it is interesting to note that the RECEIVER  of  a  message
        !           281:      can   exercise  an  extraordinary  amount  of  control  over  the
        !           282:      message's appearance.  The amount of actual control available  to
        !           283:      message  receivers  is  contingent upon the capabilities of their
        !           284:      individual message systems.
        !           285: 
        !           286: 
        !           287: 
        !           288: 
        !           289: 
        !           290:      August 13, 1982               - 2 -                      RFC #822
        !           291: 
        !           292: 
        !           293:  
        !           294:      Standard for ARPA Internet Text Messages
        !           295: 
        !           296: 
        !           297:      2.  NOTATIONAL CONVENTIONS
        !           298: 
        !           299:           This specification uses an augmented Backus-Naur Form  (BNF)
        !           300:      notation.  The differences from standard BNF involve naming rules
        !           301:      and indicating repetition and "local" alternatives.
        !           302: 
        !           303:      2.1.  RULE NAMING
        !           304: 
        !           305:           Angle brackets ("<", ">") are not  used,  in  general.   The
        !           306:      name  of  a rule is simply the name itself, rather than "<name>".
        !           307:      Quotation-marks enclose literal text (which may be  upper  and/or
        !           308:      lower  case).   Certain  basic  rules  are  in uppercase, such as
        !           309:      SPACE, TAB, CRLF, DIGIT, ALPHA, etc.  Angle brackets are used  in
        !           310:      rule  definitions,  and  in  the rest of this  document, whenever
        !           311:      their presence will facilitate discerning the use of rule names.
        !           312: 
        !           313:      2.2.  RULE1 / RULE2:  ALTERNATIVES
        !           314: 
        !           315:           Elements separated by slash ("/") are alternatives.   There-
        !           316:      fore "foo / bar" will accept foo or bar.
        !           317: 
        !           318:      2.3.  (RULE1 RULE2):  LOCAL ALTERNATIVES
        !           319: 
        !           320:           Elements enclosed in parentheses are  treated  as  a  single
        !           321:      element.   Thus,  "(elem  (foo  /  bar)  elem)"  allows the token
        !           322:      sequences "elem foo elem" and "elem bar elem".
        !           323: 
        !           324:      2.4.  *RULE:  REPETITION
        !           325: 
        !           326:           The character "*" preceding an element indicates repetition.
        !           327:      The full form is:
        !           328: 
        !           329:                               <l>*<m>element
        !           330: 
        !           331:      indicating at least <l> and at most <m> occurrences  of  element.
        !           332:      Default values are 0 and infinity so that "*(element)" allows any
        !           333:      number, including zero; "1*element" requires at  least  one;  and
        !           334:      "1*2element" allows one or two.
        !           335: 
        !           336:      2.5.  [RULE]:  OPTIONAL
        !           337: 
        !           338:           Square brackets enclose optional elements; "[foo  bar]"   is
        !           339:      equivalent to "*1(foo bar)".
        !           340: 
        !           341:      2.6.  NRULE:  SPECIFIC REPETITION
        !           342: 
        !           343:           "<n>(element)" is equivalent to "<n>*<n>(element)"; that is,
        !           344:      exactly  <n>  occurrences  of (element). Thus 2DIGIT is a 2-digit
        !           345:      number, and 3ALPHA is a string of three alphabetic characters.
        !           346: 
        !           347: 
        !           348:      August 13, 1982               - 3 -                      RFC #822
        !           349: 
        !           350: 
        !           351:  
        !           352:      Standard for ARPA Internet Text Messages
        !           353: 
        !           354: 
        !           355:      2.7.  #RULE:  LISTS
        !           356: 
        !           357:           A construct "#" is defined, similar to "*", as follows:
        !           358: 
        !           359:                               <l>#<m>element
        !           360: 
        !           361:      indicating at least <l> and at most <m> elements, each  separated
        !           362:      by  one  or more commas (","). This makes the usual form of lists
        !           363:      very easy; a rule such as '(element *("," element))' can be shown
        !           364:      as  "1#element".   Wherever this construct is used, null elements
        !           365:      are allowed, but do not  contribute  to  the  count  of  elements
        !           366:      present.   That  is,  "(element),,(element)"  is  permitted,  but
        !           367:      counts as only two elements.  Therefore, where at least one  ele-
        !           368:      ment  is required, at least one non-null element must be present.
        !           369:      Default values are 0 and infinity so that "#(element)" allows any
        !           370:      number,  including  zero;  "1#element" requires at least one; and
        !           371:      "1#2element" allows one or two.
        !           372: 
        !           373:      2.8.  ; COMMENTS
        !           374: 
        !           375:           A semi-colon, set off some distance to  the  right  of  rule
        !           376:      text,  starts  a comment that continues to the end of line.  This
        !           377:      is a simple way of including useful notes in  parallel  with  the
        !           378:      specifications.
        !           379: 
        !           380: 
        !           381: 
        !           382: 
        !           383: 
        !           384: 
        !           385: 
        !           386: 
        !           387: 
        !           388: 
        !           389: 
        !           390: 
        !           391: 
        !           392: 
        !           393: 
        !           394: 
        !           395: 
        !           396: 
        !           397: 
        !           398: 
        !           399: 
        !           400: 
        !           401: 
        !           402: 
        !           403: 
        !           404: 
        !           405: 
        !           406:      August 13, 1982               - 4 -                      RFC #822
        !           407: 
        !           408: 
        !           409:  
        !           410:      Standard for ARPA Internet Text Messages
        !           411: 
        !           412: 
        !           413:      3.  LEXICAL ANALYSIS OF MESSAGES
        !           414: 
        !           415:      3.1.  GENERAL DESCRIPTION
        !           416: 
        !           417:           A message consists of header fields and, optionally, a body.
        !           418:      The  body  is simply a sequence of lines containing ASCII charac-
        !           419:      ters.  It is separated from the headers by a null line  (i.e.,  a
        !           420:      line with nothing preceding the CRLF).
        !           421: 
        !           422:      3.1.1.  LONG HEADER FIELDS
        !           423: 
        !           424:         Each header field can be viewed as a single, logical  line  of
        !           425:         ASCII  characters,  comprising  a field-name and a field-body.
        !           426:         For convenience, the field-body  portion  of  this  conceptual
        !           427:         entity  can be split into a multiple-line representation; this
        !           428:         is called "folding".  The general rule is that wherever  there
        !           429:         may  be  linear-white-space  (NOT  simply  LWSP-chars), a CRLF
        !           430:         immediately followed by AT LEAST one LWSP-char may instead  be
        !           431:         inserted.  Thus, the single line
        !           432: 
        !           433:             To:  "Joe & J. Harvey" <ddd @Org>, JJV @ BBN
        !           434: 
        !           435:         can be represented as:
        !           436: 
        !           437:             To:  "Joe & J. Harvey" <ddd @ Org>,
        !           438:                     JJV@BBN
        !           439: 
        !           440:         and
        !           441: 
        !           442:             To:  "Joe & J. Harvey"
        !           443:                             <ddd@ Org>, JJV
        !           444:              @BBN
        !           445: 
        !           446:         and
        !           447: 
        !           448:             To:  "Joe &
        !           449:              J. Harvey" <ddd @ Org>, JJV @ BBN
        !           450: 
        !           451:              The process of moving  from  this  folded   multiple-line
        !           452:         representation  of a header field to its single line represen-
        !           453:         tation is called "unfolding".  Unfolding  is  accomplished  by
        !           454:         regarding   CRLF   immediately  followed  by  a  LWSP-char  as
        !           455:         equivalent to the LWSP-char.
        !           456: 
        !           457:         Note:  While the standard  permits  folding  wherever  linear-
        !           458:                white-space is permitted, it is recommended that struc-
        !           459:                tured fields, such as those containing addresses, limit
        !           460:                folding  to higher-level syntactic breaks.  For address
        !           461:                fields, it  is  recommended  that  such  folding  occur
        !           462: 
        !           463: 
        !           464:      August 13, 1982               - 5 -                      RFC #822
        !           465: 
        !           466: 
        !           467:  
        !           468:      Standard for ARPA Internet Text Messages
        !           469: 
        !           470: 
        !           471:                between addresses, after the separating comma.
        !           472: 
        !           473:      3.1.2.  STRUCTURE OF HEADER FIELDS
        !           474: 
        !           475:         Once a field has been unfolded, it may be viewed as being com-
        !           476:         posed of a field-name followed by a colon (":"), followed by a
        !           477:         field-body, and  terminated  by  a  carriage-return/line-feed.
        !           478:         The  field-name must be composed of printable ASCII characters
        !           479:         (i.e., characters that  have  values  between  33.  and  126.,
        !           480:         decimal, except colon).  The field-body may be composed of any
        !           481:         ASCII characters, except CR or LF.  (While CR and/or LF may be
        !           482:         present  in the actual text, they are removed by the action of
        !           483:         unfolding the field.)
        !           484: 
        !           485:         Certain field-bodies of headers may be  interpreted  according
        !           486:         to  an  internal  syntax  that some systems may wish to parse.
        !           487:         These  fields  are  called  "structured   fields".    Examples
        !           488:         include  fields containing dates and addresses.  Other fields,
        !           489:         such as "Subject"  and  "Comments",  are  regarded  simply  as
        !           490:         strings of text.
        !           491: 
        !           492:         Note:  Any field which has a field-body  that  is  defined  as
        !           493:                other  than  simply <text> is to be treated as a struc-
        !           494:                tured field.
        !           495: 
        !           496:                Field-names, unstructured field bodies  and  structured
        !           497:                field bodies each are scanned by their own, independent
        !           498:                "lexical" analyzers.
        !           499: 
        !           500:      3.1.3.  UNSTRUCTURED FIELD BODIES
        !           501: 
        !           502:         For some fields, such as "Subject" and "Comments",  no  struc-
        !           503:         turing  is assumed, and they are treated simply as <text>s, as
        !           504:         in the message body.  Rules of folding apply to these  fields,
        !           505:         so  that  such  field  bodies  which occupy several lines must
        !           506:         therefore have the second and successive lines indented by  at
        !           507:         least one LWSP-char.
        !           508: 
        !           509:      3.1.4.  STRUCTURED FIELD BODIES
        !           510: 
        !           511:         To aid in the creation and reading of structured  fields,  the
        !           512:         free  insertion   of linear-white-space (which permits folding
        !           513:         by inclusion of CRLFs)  is  allowed  between  lexical  tokens.
        !           514:         Rather  than  obscuring  the  syntax  specifications for these
        !           515:         structured fields with explicit syntax for this  linear-white-
        !           516:         space, the existence of another "lexical" analyzer is assumed.
        !           517:         This analyzer does not apply  for  unstructured  field  bodies
        !           518:         that  are  simply  strings  of  text, as described above.  The
        !           519:         analyzer provides  an  interpretation  of  the  unfolded  text
        !           520: 
        !           521: 
        !           522:      August 13, 1982               - 6 -                      RFC #822
        !           523: 
        !           524: 
        !           525:  
        !           526:      Standard for ARPA Internet Text Messages
        !           527: 
        !           528: 
        !           529:         composing  the body of the field as a sequence of lexical sym-
        !           530:         bols.
        !           531: 
        !           532:         These symbols are:
        !           533: 
        !           534:                      -  individual special characters
        !           535:                      -  quoted-strings
        !           536:                      -  domain-literals
        !           537:                      -  comments
        !           538:                      -  atoms
        !           539: 
        !           540:         The first four of these symbols  are  self-delimiting.   Atoms
        !           541:         are not; they are delimited by the self-delimiting symbols and
        !           542:         by  linear-white-space.   For  the  purposes  of  regenerating
        !           543:         sequences  of  atoms  and quoted-strings, exactly one SPACE is
        !           544:         assumed to exist, and should be used, between them.  (Also, in
        !           545:         the "Clarifications" section on "White Space", below, note the
        !           546:         rules about treatment of multiple contiguous LWSP-chars.)
        !           547: 
        !           548:         So, for example, the folded body of an address field
        !           549: 
        !           550:             ":sysmail"@  Some-Group. Some-Org,
        !           551:             Muhammed.(I am  the greatest) Ali @(the)Vegas.WBA
        !           552: 
        !           553: 
        !           554: 
        !           555: 
        !           556: 
        !           557: 
        !           558: 
        !           559: 
        !           560: 
        !           561: 
        !           562: 
        !           563: 
        !           564: 
        !           565: 
        !           566: 
        !           567: 
        !           568: 
        !           569: 
        !           570: 
        !           571: 
        !           572: 
        !           573: 
        !           574: 
        !           575: 
        !           576: 
        !           577: 
        !           578: 
        !           579: 
        !           580:      August 13, 1982               - 7 -                      RFC #822
        !           581: 
        !           582: 
        !           583:  
        !           584:      Standard for ARPA Internet Text Messages
        !           585: 
        !           586: 
        !           587:         is analyzed into the following lexical symbols and types:
        !           588: 
        !           589:                     :sysmail              quoted string
        !           590:                     @                     special
        !           591:                     Some-Group            atom
        !           592:                     .                     special
        !           593:                     Some-Org              atom
        !           594:                     ,                     special
        !           595:                     Muhammed              atom
        !           596:                     .                     special
        !           597:                     (I am  the greatest)  comment
        !           598:                     Ali                   atom
        !           599:                     @                     atom
        !           600:                     (the)                 comment
        !           601:                     Vegas                 atom
        !           602:                     .                     special
        !           603:                     WBA                   atom
        !           604: 
        !           605:         The canonical representations for the data in these  addresses
        !           606:         are the following strings:
        !           607: 
        !           608:                         ":sysmail"@Some-Group.Some-Org
        !           609: 
        !           610:         and
        !           611: 
        !           612:                             [email protected]
        !           613: 
        !           614:         Note:  For purposes of display, and when passing  such  struc-
        !           615:                tured information to other systems, such as mail proto-
        !           616:                col  services,  there  must  be  NO  linear-white-space
        !           617:                between  <word>s  that are separated by period (".") or
        !           618:                at-sign ("@") and exactly one SPACE between  all  other
        !           619:                <word>s.  Also, headers should be in a folded form.
        !           620: 
        !           621: 
        !           622: 
        !           623: 
        !           624: 
        !           625: 
        !           626: 
        !           627: 
        !           628: 
        !           629: 
        !           630: 
        !           631: 
        !           632: 
        !           633: 
        !           634: 
        !           635: 
        !           636: 
        !           637: 
        !           638:      August 13, 1982               - 8 -                      RFC #822
        !           639: 
        !           640: 
        !           641:  
        !           642:      Standard for ARPA Internet Text Messages
        !           643: 
        !           644: 
        !           645:      3.2.  HEADER FIELD DEFINITIONS
        !           646: 
        !           647:           These rules show a field meta-syntax, without regard for the
        !           648:      particular  type  or internal syntax.  Their purpose is to permit
        !           649:      detection of fields; also, they present to  higher-level  parsers
        !           650:      an image of each field as fitting on one line.
        !           651: 
        !           652:      field       =  field-name ":" [ field-body ] CRLF
        !           653: 
        !           654:      field-name  =  1*<any CHAR, excluding CTLs, SPACE, and ":">
        !           655: 
        !           656:      field-body  =  field-body-contents
        !           657:                     [CRLF LWSP-char field-body]
        !           658: 
        !           659:      field-body-contents =
        !           660:                    <the ASCII characters making up the field-body, as
        !           661:                     defined in the following sections, and consisting
        !           662:                     of combinations of atom, quoted-string, and
        !           663:                     specials tokens, or else consisting of texts>
        !           664: 
        !           665: 
        !           666: 
        !           667: 
        !           668: 
        !           669: 
        !           670: 
        !           671: 
        !           672: 
        !           673: 
        !           674: 
        !           675: 
        !           676: 
        !           677: 
        !           678: 
        !           679: 
        !           680: 
        !           681: 
        !           682: 
        !           683: 
        !           684: 
        !           685: 
        !           686: 
        !           687: 
        !           688: 
        !           689: 
        !           690: 
        !           691: 
        !           692: 
        !           693: 
        !           694: 
        !           695: 
        !           696:      August 13, 1982               - 9 -                      RFC #822
        !           697: 
        !           698: 
        !           699:  
        !           700:      Standard for ARPA Internet Text Messages
        !           701: 
        !           702: 
        !           703:      3.3.  LEXICAL TOKENS
        !           704: 
        !           705:           The following rules are used to define an underlying lexical
        !           706:      analyzer,  which  feeds  tokens to higher level parsers.  See the
        !           707:      ANSI references, in the Bibliography.
        !           708: 
        !           709:                                                  ; (  Octal, Decimal.)
        !           710:      CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
        !           711:      ALPHA       =  <any ASCII alphabetic character>
        !           712:                                                  ; (101-132, 65.- 90.)
        !           713:                                                  ; (141-172, 97.-122.)
        !           714:      DIGIT       =  <any ASCII decimal digit>    ; ( 60- 71, 48.- 57.)
        !           715:      CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
        !           716:                      character and DEL>          ; (    177,     127.)
        !           717:      CR          =  <ASCII CR, carriage return>  ; (     15,      13.)
        !           718:      LF          =  <ASCII LF, linefeed>         ; (     12,      10.)
        !           719:      SPACE       =  <ASCII SP, space>            ; (     40,      32.)
        !           720:      HTAB        =  <ASCII HT, horizontal-tab>   ; (     11,       9.)
        !           721:      <">         =  <ASCII quote mark>           ; (     42,      34.)
        !           722:      CRLF        =  CR LF
        !           723: 
        !           724:      LWSP-char   =  SPACE / HTAB                 ; semantics = SPACE
        !           725: 
        !           726:      linear-white-space =  1*([CRLF] LWSP-char)  ; semantics = SPACE
        !           727:                                                  ; CRLF => folding
        !           728: 
        !           729:      specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
        !           730:                  /  "," / ";" / ":" / "\" / <">  ;  string, to use
        !           731:                  /  "." / "[" / "]"              ;  within a word.
        !           732: 
        !           733:      delimiters  =  specials / linear-white-space / comment
        !           734: 
        !           735:      text        =  <any CHAR, including bare    ; => atoms, specials,
        !           736:                      CR & bare LF, but NOT       ;  comments and
        !           737:                      including CRLF>             ;  quoted-strings are
        !           738:                                                  ;  NOT recognized.
        !           739: 
        !           740:      atom        =  1*<any CHAR except specials, SPACE and CTLs>
        !           741: 
        !           742:      quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
        !           743:                                                  ;   quoted chars.
        !           744: 
        !           745:      qtext       =  <any CHAR excepting <">,     ; => may be folded
        !           746:                      "\" & CR, and including
        !           747:                      linear-white-space>
        !           748: 
        !           749:      domain-literal =  "[" *(dtext / quoted-pair) "]"
        !           750: 
        !           751: 
        !           752: 
        !           753: 
        !           754:      August 13, 1982              - 10 -                      RFC #822
        !           755: 
        !           756: 
        !           757:  
        !           758:      Standard for ARPA Internet Text Messages
        !           759: 
        !           760: 
        !           761:      dtext       =  <any CHAR excluding "[",     ; => may be folded
        !           762:                      "]", "\" & CR, & including
        !           763:                      linear-white-space>
        !           764: 
        !           765:      comment     =  "(" *(ctext / quoted-pair / comment) ")"
        !           766: 
        !           767:      ctext       =  <any CHAR excluding "(",     ; => may be folded
        !           768:                      ")", "\" & CR, & including
        !           769:                      linear-white-space>
        !           770: 
        !           771:      quoted-pair =  "\" CHAR                     ; may quote any char
        !           772: 
        !           773:      phrase      =  1*word                       ; Sequence of words
        !           774: 
        !           775:      word        =  atom / quoted-string
        !           776: 
        !           777: 
        !           778:      3.4.  CLARIFICATIONS
        !           779: 
        !           780:      3.4.1.  QUOTING
        !           781: 
        !           782:         Some characters are reserved for special interpretation,  such
        !           783:         as  delimiting lexical tokens.  To permit use of these charac-
        !           784:         ters as uninterpreted data, a quoting mechanism  is  provided.
        !           785:         To quote a character, precede it with a backslash ("\").
        !           786: 
        !           787:         This mechanism is not fully general.  Characters may be quoted
        !           788:         only  within  a subset of the lexical constructs.  In particu-
        !           789:         lar, quoting is limited to use within:
        !           790: 
        !           791:                              -  quoted-string
        !           792:                              -  domain-literal
        !           793:                              -  comment
        !           794: 
        !           795:         Within these constructs, quoting is REQUIRED for  CR  and  "\"
        !           796:         and for the character(s) that delimit the token (e.g., "(" and
        !           797:         ")" for a comment).  However, quoting  is  PERMITTED  for  any
        !           798:         character.
        !           799: 
        !           800:         Note:  In particular, quoting is NOT permitted  within  atoms.
        !           801:                For  example  when  the local-part of an addr-spec must
        !           802:                contain a special character, a quoted  string  must  be
        !           803:                used.  Therefore, a specification such as:
        !           804: 
        !           805:                             Full\ Name@Domain
        !           806: 
        !           807:                is not legal and must be specified as:
        !           808: 
        !           809:                             "Full Name"@Domain
        !           810: 
        !           811: 
        !           812:      August 13, 1982              - 11 -                      RFC #822
        !           813: 
        !           814: 
        !           815:  
        !           816:      Standard for ARPA Internet Text Messages
        !           817: 
        !           818: 
        !           819:      3.4.2.  WHITE SPACE
        !           820: 
        !           821:         Note:  In structured field bodies, multiple linear space ASCII
        !           822:                characters  (namely  HTABs  and  SPACEs) are treated as
        !           823:                single spaces and may freely surround any  symbol.   In
        !           824:                all header fields, the only place in which at least one
        !           825:                LWSP-char is REQUIRED is at the beginning of  continua-
        !           826:                tion lines in a folded field.
        !           827: 
        !           828:         When passing text to processes  that  do  not  interpret  text
        !           829:         according to this standard (e.g., mail protocol servers), then
        !           830:         NO linear-white-space characters should occur between a period
        !           831:         (".") or at-sign ("@") and a <word>.  Exactly ONE SPACE should
        !           832:         be used in place of arbitrary linear-white-space  and  comment
        !           833:         sequences.
        !           834: 
        !           835:         Note:  Within systems conforming to this standard, wherever  a
        !           836:                member of the list of delimiters is allowed, LWSP-chars
        !           837:                may also occur before and/or after it.
        !           838: 
        !           839:         Writers of  mail-sending  (i.e.,  header-generating)  programs
        !           840:         should realize that there is no network-wide definition of the
        !           841:         effect of ASCII HT (horizontal-tab) characters on the  appear-
        !           842:         ance  of  text  at another network host; therefore, the use of
        !           843:         tabs in message headers, though permitted, is discouraged.
        !           844: 
        !           845:      3.4.3.  COMMENTS
        !           846: 
        !           847:         A comment is a set of ASCII characters, which is  enclosed  in
        !           848:         matching  parentheses  and which is not within a quoted-string
        !           849:         The comment construct permits message originators to add  text
        !           850:         which  will  be  useful  for  human readers, but which will be
        !           851:         ignored by the formal semantics.  Comments should be  retained
        !           852:         while  the  message  is subject to interpretation according to
        !           853:         this standard.  However, comments  must  NOT  be  included  in
        !           854:         other  cases,  such  as  during  protocol  exchanges with mail
        !           855:         servers.
        !           856: 
        !           857:         Comments nest, so that if an unquoted left parenthesis  occurs
        !           858:         in  a  comment  string,  there  must  also be a matching right
        !           859:         parenthesis.  When a comment acts as the delimiter  between  a
        !           860:         sequence of two lexical symbols, such as two atoms, it is lex-
        !           861:         ically equivalent with a single SPACE,  for  the  purposes  of
        !           862:         regenerating  the  sequence, such as when passing the sequence
        !           863:         onto a mail protocol server.  Comments are  detected  as  such
        !           864:         only within field-bodies of structured fields.
        !           865: 
        !           866:         If a comment is to be "folded" onto multiple lines,  then  the
        !           867:         syntax  for  folding  must  be  adhered to.  (See the "Lexical
        !           868: 
        !           869: 
        !           870:      August 13, 1982              - 12 -                      RFC #822
        !           871: 
        !           872: 
        !           873:  
        !           874:      Standard for ARPA Internet Text Messages
        !           875: 
        !           876: 
        !           877:         Analysis of Messages" section on "Folding Long Header  Fields"
        !           878:         above,  and  the  section on "Case Independence" below.)  Note
        !           879:         that  the  official  semantics  therefore  do  not  "see"  any
        !           880:         unquoted CRLFs that are in comments, although particular pars-
        !           881:         ing programs may wish to note their presence.  For these  pro-
        !           882:         grams,  it would be reasonable to interpret a "CRLF LWSP-char"
        !           883:         as being a CRLF that is part of the comment; i.e., the CRLF is
        !           884:         kept  and  the  LWSP-char is discarded.  Quoted CRLFs (i.e., a
        !           885:         backslash followed by a CR followed by a  LF)  still  must  be
        !           886:         followed by at least one LWSP-char.
        !           887: 
        !           888:      3.4.4.  DELIMITING AND QUOTING CHARACTERS
        !           889: 
        !           890:         The quote character (backslash) and  characters  that  delimit
        !           891:         syntactic  units  are not, generally, to be taken as data that
        !           892:         are part of the delimited or quoted unit(s).   In  particular,
        !           893:         the   quotation-marks   that   define   a  quoted-string,  the
        !           894:         parentheses that define  a  comment  and  the  backslash  that
        !           895:         quotes  a  following  character  are  NOT  part of the quoted-
        !           896:         string, comment or quoted character.  A quotation-mark that is
        !           897:         to  be  part  of  a quoted-string, a parenthesis that is to be
        !           898:         part of a comment and a backslash that is to be part of either
        !           899:         must  each be preceded by the quote-character backslash ("\").
        !           900:         Note that the syntax allows any character to be quoted  within
        !           901:         a  quoted-string  or  comment; however only certain characters
        !           902:         MUST be quoted to be included as data.  These  characters  are
        !           903:         the  ones that are not part of the alternate text group (i.e.,
        !           904:         ctext or qtext).
        !           905: 
        !           906:         The one exception to this rule  is  that  a  single  SPACE  is
        !           907:         assumed  to  exist  between  contiguous words in a phrase, and
        !           908:         this interpretation is independent of  the  actual  number  of
        !           909:         LWSP-chars  that  the  creator  places  between the words.  To
        !           910:         include more than one SPACE, the creator must make  the  LWSP-
        !           911:         chars be part of a quoted-string.
        !           912: 
        !           913:         Quotation marks that delimit a quoted string  and  backslashes
        !           914:         that  quote  the  following character should NOT accompany the
        !           915:         quoted-string when the string is passed to processes  that  do
        !           916:         not interpret data according to this specification (e.g., mail
        !           917:         protocol servers).
        !           918: 
        !           919:      3.4.5.  QUOTED-STRINGS
        !           920: 
        !           921:         Where permitted (i.e., in words in structured fields)  quoted-
        !           922:         strings  are  treated  as a single symbol.  That is, a quoted-
        !           923:         string is equivalent to an atom, syntactically.  If a  quoted-
        !           924:         string  is to be "folded" onto multiple lines, then the syntax
        !           925:         for folding must be adhered to.  (See the "Lexical Analysis of
        !           926: 
        !           927: 
        !           928:      August 13, 1982              - 13 -                      RFC #822
        !           929: 
        !           930: 
        !           931:  
        !           932:      Standard for ARPA Internet Text Messages
        !           933: 
        !           934: 
        !           935:         Messages"  section  on "Folding Long Header Fields" above, and
        !           936:         the section on "Case  Independence"  below.)   Therefore,  the
        !           937:         official  semantics  do  not  "see" any bare CRLFs that are in
        !           938:         quoted-strings; however particular parsing programs  may  wish
        !           939:         to  note  their presence.  For such programs, it would be rea-
        !           940:         sonable to interpret a "CRLF LWSP-char" as being a CRLF  which
        !           941:         is  part  of the quoted-string; i.e., the CRLF is kept and the
        !           942:         LWSP-char is discarded.  Quoted CRLFs (i.e., a backslash  fol-
        !           943:         lowed  by  a CR followed by a LF) are also subject to rules of
        !           944:         folding, but the presence of the quoting character (backslash)
        !           945:         explicitly  indicates  that  the  CRLF  is  data to the quoted
        !           946:         string.  Stripping off the first following LWSP-char  is  also
        !           947:         appropriate when parsing quoted CRLFs.
        !           948: 
        !           949:      3.4.6.  BRACKETING CHARACTERS
        !           950: 
        !           951:         There is one type of bracket which must occur in matched pairs
        !           952:         and may have pairs nested within each other:
        !           953: 
        !           954:             o   Parentheses ("(" and ")") are used  to  indicate  com-
        !           955:                 ments.
        !           956: 
        !           957:         There are three types of brackets which must occur in  matched
        !           958:         pairs, and which may NOT be nested:
        !           959: 
        !           960:             o   Colon/semi-colon (":" and ";") are   used  in  address
        !           961:                 specifications  to  indicate that the included list of
        !           962:                 addresses are to be treated as a group.
        !           963: 
        !           964:             o   Angle brackets ("<" and ">")  are  generally  used  to
        !           965:                 indicate  the  presence of a one machine-usable refer-
        !           966:                 ence (e.g., delimiting mailboxes), possibly  including
        !           967:                 source-routing to the machine.
        !           968: 
        !           969:             o   Square brackets ("[" and "]") are used to indicate the
        !           970:                 presence  of  a  domain-literal, which the appropriate
        !           971:                 name-domain  is  to  use  directly,  bypassing  normal
        !           972:                 name-resolution mechanisms.
        !           973: 
        !           974:      3.4.7.  CASE INDEPENDENCE
        !           975: 
        !           976:         Except as noted, alphabetic strings may be represented in  any
        !           977:         combination of upper and lower case.  The only syntactic units
        !           978: 
        !           979: 
        !           980: 
        !           981: 
        !           982: 
        !           983: 
        !           984: 
        !           985: 
        !           986:      August 13, 1982              - 14 -                      RFC #822
        !           987: 
        !           988: 
        !           989:  
        !           990:      Standard for ARPA Internet Text Messages
        !           991: 
        !           992: 
        !           993:         which requires preservation of case information are:
        !           994: 
        !           995:                     -  text
        !           996:                     -  qtext
        !           997:                     -  dtext
        !           998:                     -  ctext
        !           999:                     -  quoted-pair
        !          1000:                     -  local-part, except "Postmaster"
        !          1001: 
        !          1002:         When matching any other syntactic unit, case is to be ignored.
        !          1003:         For  example, the field-names "From", "FROM", "from", and even
        !          1004:         "FroM" are semantically equal and should all be treated ident-
        !          1005:         ically.
        !          1006: 
        !          1007:         When generating these units, any mix of upper and  lower  case
        !          1008:         alphabetic  characters  may  be  used.  The case shown in this
        !          1009:         specification is suggested for message-creating processes.
        !          1010: 
        !          1011:         Note:  The reserved local-part address unit, "Postmaster",  is
        !          1012:                an  exception.   When  the  value "Postmaster" is being
        !          1013:                interpreted, it must be  accepted  in  any  mixture  of
        !          1014:                case, including "POSTMASTER", and "postmaster".
        !          1015: 
        !          1016:      3.4.8.  FOLDING LONG HEADER FIELDS
        !          1017: 
        !          1018:         Each header field may be represented on exactly one line  con-
        !          1019:         sisting  of the name of the field and its body, and terminated
        !          1020:         by a CRLF; this is what the parser sees.  For readability, the
        !          1021:         field-body  portion of long header fields may be "folded" onto
        !          1022:         multiple lines of the actual field.  "Long" is commonly inter-
        !          1023:         preted  to  mean greater than 65 or 72 characters.  The former
        !          1024:         length serves as a limit, when the message is to be viewed  on
        !          1025:         most  simple terminals which use simple display software; how-
        !          1026:         ever, the limit is not imposed by this standard.
        !          1027: 
        !          1028:         Note:  Some display software often can selectively fold lines,
        !          1029:                to  suit  the display terminal.  In such cases, sender-
        !          1030:                provided  folding  can  interfere  with   the   display
        !          1031:                software.
        !          1032: 
        !          1033:      3.4.9.  BACKSPACE CHARACTERS
        !          1034: 
        !          1035:         ASCII BS characters (Backspace, decimal 8) may be included  in
        !          1036:         texts and quoted-strings to effect overstriking.  However, any
        !          1037:         use of backspaces which effects an overstrike to the  left  of
        !          1038:         the beginning of the text or quoted-string is prohibited.
        !          1039: 
        !          1040: 
        !          1041: 
        !          1042: 
        !          1043: 
        !          1044:      August 13, 1982              - 15 -                      RFC #822
        !          1045: 
        !          1046: 
        !          1047:  
        !          1048:      Standard for ARPA Internet Text Messages
        !          1049: 
        !          1050: 
        !          1051:      3.4.10.  NETWORK-SPECIFIC TRANSFORMATIONS
        !          1052: 
        !          1053:         During transmission through heterogeneous networks, it may  be
        !          1054:         necessary  to  force data to conform to a network's local con-
        !          1055:         ventions.  For example, it may be required that a CR  be  fol-
        !          1056:         lowed  either by LF, making a CRLF, or by <null>, if the CR is
        !          1057:         to stand alone).  Such transformations are reversed, when  the
        !          1058:         message exits that network.
        !          1059: 
        !          1060:         When  crossing  network  boundaries,  the  message  should  be
        !          1061:         treated  as  passing  through  two modules.  It will enter the
        !          1062:         first module containing whatever network-specific  transforma-
        !          1063:         tions  that  were  necessary  to  permit migration through the
        !          1064:         "current" network.  It then passes through the modules:
        !          1065: 
        !          1066:             o   Transformation Reversal
        !          1067: 
        !          1068:                 The "current" network's idiosyncracies are removed and
        !          1069:                 the  message  is returned to the canonical form speci-
        !          1070:                 fied in this standard.
        !          1071: 
        !          1072:             o   Transformation
        !          1073: 
        !          1074:                 The "next" network's local idiosyncracies are  imposed
        !          1075:                 on the message.
        !          1076: 
        !          1077:                                 ------------------
        !          1078:                     From   ==>  | Remove Net-A   |
        !          1079:                     Net-A       | idiosyncracies |
        !          1080:                                 ------------------
        !          1081:                                        ||
        !          1082:                                        \/
        !          1083:                                   Conformance
        !          1084:                                   with standard
        !          1085:                                        ||
        !          1086:                                        \/
        !          1087:                                 ------------------
        !          1088:                                 | Impose Net-B   |  ==>  To
        !          1089:                                 | idiosyncracies |       Net-B
        !          1090:                                 ------------------
        !          1091: 
        !          1092: 
        !          1093: 
        !          1094: 
        !          1095: 
        !          1096: 
        !          1097: 
        !          1098: 
        !          1099: 
        !          1100: 
        !          1101: 
        !          1102:      August 13, 1982              - 16 -                      RFC #822
        !          1103: 
        !          1104: 
        !          1105:  
        !          1106:      Standard for ARPA Internet Text Messages
        !          1107: 
        !          1108: 
        !          1109:      4.  MESSAGE SPECIFICATION
        !          1110: 
        !          1111:      4.1.  SYNTAX
        !          1112: 
        !          1113:      Note:  Due to an artifact of the notational conventions, the syn-
        !          1114:             tax  indicates that, when present, some fields, must be in
        !          1115:             a particular order.  Header fields  are  NOT  required  to
        !          1116:             occur  in  any  particular  order, except that the message
        !          1117:             body must occur AFTER  the  headers.   It  is  recommended
        !          1118:             that,  if  present,  headers be sent in the order "Return-
        !          1119:             Path", "Received", "Date",  "From",  "Subject",  "Sender",
        !          1120:             "To", "cc", etc.
        !          1121: 
        !          1122:             This specification permits multiple  occurrences  of  most
        !          1123:             fields.   Except  as  noted,  their  interpretation is not
        !          1124:             specified here, and their use is discouraged.
        !          1125: 
        !          1126:           The following syntax for the bodies of various fields should
        !          1127:      be  thought  of  as  describing  each field body as a single long
        !          1128:      string (or line).  The "Lexical Analysis of Message"  section  on
        !          1129:      "Long  Header Fields", above, indicates how such long strings can
        !          1130:      be represented on more than one line in  the  actual  transmitted
        !          1131:      message.
        !          1132: 
        !          1133:      message     =  fields *( CRLF *text )       ; Everything after
        !          1134:                                                  ;  first null line
        !          1135:                                                  ;  is message body
        !          1136: 
        !          1137:      fields      =    dates                      ; Creation time,
        !          1138:                       source                     ;  author id & one
        !          1139:                     1*destination                ;  address required
        !          1140:                      *optional-field             ;  others optional
        !          1141: 
        !          1142:      source      = [  trace ]                    ; net traversals
        !          1143:                       originator                 ; original mail
        !          1144:                    [  resent ]                   ; forwarded
        !          1145: 
        !          1146:      trace       =    return                     ; path to sender
        !          1147:                     1*received                   ; receipt tags
        !          1148: 
        !          1149:      return      =  "Return-path" ":" route-addr ; return address
        !          1150: 
        !          1151:      received    =  "Received"    ":"            ; one per relay
        !          1152:                        ["from" domain]           ; sending host
        !          1153:                        ["by"   domain]           ; receiving host
        !          1154:                        ["via"  atom]             ; physical path
        !          1155:                       *("with" atom)             ; link/mail protocol
        !          1156:                        ["id"   msg-id]           ; receiver msg id
        !          1157:                        ["for"  addr-spec]        ; initial form
        !          1158: 
        !          1159: 
        !          1160:      August 13, 1982              - 17 -                      RFC #822
        !          1161: 
        !          1162: 
        !          1163:  
        !          1164:      Standard for ARPA Internet Text Messages
        !          1165: 
        !          1166: 
        !          1167:                         ";"    date-time         ; time received
        !          1168: 
        !          1169:      originator  =   authentic                   ; authenticated addr
        !          1170:                    [ "Reply-To"   ":" 1#address] )
        !          1171: 
        !          1172:      authentic   =   "From"       ":"   mailbox  ; Single author
        !          1173:                  / ( "Sender"     ":"   mailbox  ; Actual submittor
        !          1174:                      "From"       ":" 1#mailbox) ; Multiple authors
        !          1175:                                                  ;  or not sender
        !          1176: 
        !          1177:      resent      =   resent-authentic
        !          1178:                    [ "Resent-Reply-To"  ":" 1#address] )
        !          1179: 
        !          1180:      resent-authentic =
        !          1181:                  =   "Resent-From"      ":"   mailbox
        !          1182:                  / ( "Resent-Sender"    ":"   mailbox
        !          1183:                      "Resent-From"      ":" 1#mailbox  )
        !          1184: 
        !          1185:      dates       =   orig-date                   ; Original
        !          1186:                    [ resent-date ]               ; Forwarded
        !          1187: 
        !          1188:      orig-date   =  "Date"        ":"   date-time
        !          1189: 
        !          1190:      resent-date =  "Resent-Date" ":"   date-time
        !          1191: 
        !          1192:      destination =  "To"          ":" 1#address  ; Primary
        !          1193:                  /  "Resent-To"   ":" 1#address
        !          1194:                  /  "cc"          ":" 1#address  ; Secondary
        !          1195:                  /  "Resent-cc"   ":" 1#address
        !          1196:                  /  "bcc"         ":"  #address  ; Blind carbon
        !          1197:                  /  "Resent-bcc"  ":"  #address
        !          1198: 
        !          1199:      optional-field =
        !          1200:                  /  "Message-ID"        ":"   msg-id
        !          1201:                  /  "Resent-Message-ID" ":"   msg-id
        !          1202:                  /  "In-Reply-To"       ":"  *(phrase / msg-id)
        !          1203:                  /  "References"        ":"  *(phrase / msg-id)
        !          1204:                  /  "Keywords"          ":"  #phrase
        !          1205:                  /  "Subject"           ":"  *text
        !          1206:                  /  "Comments"          ":"  *text
        !          1207:                  /  "Encrypted"         ":" 1#2word
        !          1208:                  /  extension-field              ; To be defined
        !          1209:                  /  user-defined-field           ; May be pre-empted
        !          1210: 
        !          1211:      msg-id      =  "<" addr-spec ">"            ; Unique message id
        !          1212: 
        !          1213: 
        !          1214: 
        !          1215: 
        !          1216: 
        !          1217: 
        !          1218:      August 13, 1982              - 18 -                      RFC #822
        !          1219: 
        !          1220: 
        !          1221:  
        !          1222:      Standard for ARPA Internet Text Messages
        !          1223: 
        !          1224: 
        !          1225:      extension-field =
        !          1226:                    <Any field which is defined in a document
        !          1227:                     published as a formal extension to this
        !          1228:                     specification; none will have names beginning
        !          1229:                     with the string "X-">
        !          1230: 
        !          1231:      user-defined-field =
        !          1232:                    <Any field which has not been defined
        !          1233:                     in this specification or published as an
        !          1234:                     extension to this specification; names for
        !          1235:                     such fields must be unique and may be
        !          1236:                     pre-empted by published extensions>
        !          1237: 
        !          1238:      4.2.  FORWARDING
        !          1239: 
        !          1240:           Some systems permit mail recipients to  forward  a  message,
        !          1241:      retaining  the original headers, by adding some new fields.  This
        !          1242:      standard supports such a service, through the "Resent-" prefix to
        !          1243:      field names.
        !          1244: 
        !          1245:           Whenever the string "Resent-" begins a field name, the field
        !          1246:      has  the  same  semantics as a field whose name does not have the
        !          1247:      prefix.  However, the message is assumed to have  been  forwarded
        !          1248:      by  an original recipient who attached the "Resent-" field.  This
        !          1249:      new field is treated as being more recent  than  the  equivalent,
        !          1250:      original  field.   For  example, the "Resent-From", indicates the
        !          1251:      person that forwarded the message, whereas the "From" field indi-
        !          1252:      cates the original author.
        !          1253: 
        !          1254:           Use of such precedence  information  depends  upon  partici-
        !          1255:      pants'  communication needs.  For example, this standard does not
        !          1256:      dictate when a "Resent-From:" address should receive replies,  in
        !          1257:      lieu of sending them to the "From:" address.
        !          1258: 
        !          1259:      Note:  In general, the "Resent-" fields should be treated as con-
        !          1260:             taining  a  set  of information that is independent of the
        !          1261:             set of original fields.  Information for  one  set  should
        !          1262:             not  automatically be taken from the other.  The interpre-
        !          1263:             tation of multiple "Resent-" fields, of the same type,  is
        !          1264:             undefined.
        !          1265: 
        !          1266:           In the remainder of this specification, occurrence of  legal
        !          1267:      "Resent-"  fields  are treated identically with the occurrence of
        !          1268: 
        !          1269: 
        !          1270: 
        !          1271: 
        !          1272: 
        !          1273: 
        !          1274: 
        !          1275: 
        !          1276:      August 13, 1982              - 19 -                      RFC #822
        !          1277: 
        !          1278: 
        !          1279:  
        !          1280:      Standard for ARPA Internet Text Messages
        !          1281: 
        !          1282: 
        !          1283:      fields whose names do not contain this prefix.
        !          1284: 
        !          1285:      4.3.  TRACE FIELDS
        !          1286: 
        !          1287:           Trace information is used to provide an audit trail of  mes-
        !          1288:      sage  handling.   In  addition,  it indicates a route back to the
        !          1289:      sender of the message.
        !          1290: 
        !          1291:           The list of known "via" and  "with"  values  are  registered
        !          1292:      with  the  Network  Information  Center, SRI International, Menlo
        !          1293:      Park, California.
        !          1294: 
        !          1295:      4.3.1.  RETURN-PATH
        !          1296: 
        !          1297:         This field  is  added  by  the  final  transport  system  that
        !          1298:         delivers  the message to its recipient.  The field is intended
        !          1299:         to contain definitive information about the address and  route
        !          1300:         back to the message's originator.
        !          1301: 
        !          1302:         Note:  The "Reply-To" field is added  by  the  originator  and
        !          1303:                serves  to  direct  replies,  whereas the "Return-Path"
        !          1304:                field is used to identify a path back to  the  origina-
        !          1305:                tor.
        !          1306: 
        !          1307:         While the syntax  indicates  that  a  route  specification  is
        !          1308:         optional,  every attempt should be made to provide that infor-
        !          1309:         mation in this field.
        !          1310: 
        !          1311:      4.3.2.  RECEIVED
        !          1312: 
        !          1313:         A copy of this field is added by each transport  service  that
        !          1314:         relays the message.  The information in the field can be quite
        !          1315:         useful for tracing transport problems.
        !          1316: 
        !          1317:         The names of the sending  and  receiving  hosts  and  time-of-
        !          1318:         receipt may be specified.  The "via" parameter may be used, to
        !          1319:         indicate what physical mechanism the message  was  sent  over,
        !          1320:         such  as  Arpanet or Phonenet, and the "with" parameter may be
        !          1321:         used to indicate the mail-,  or  connection-,  level  protocol
        !          1322:         that  was  used, such as the SMTP mail protocol, or X.25 tran-
        !          1323:         sport protocol.
        !          1324: 
        !          1325:         Note:  Several "with" parameters may  be  included,  to  fully
        !          1326:                specify the set of protocols that were used.
        !          1327: 
        !          1328:         Some transport services queue mail; the internal message iden-
        !          1329:         tifier that is assigned to the message may be noted, using the
        !          1330:         "id" parameter.  When the  sending  host  uses  a  destination
        !          1331:         address specification that the receiving host reinterprets, by
        !          1332: 
        !          1333: 
        !          1334:      August 13, 1982              - 20 -                      RFC #822
        !          1335: 
        !          1336: 
        !          1337:  
        !          1338:      Standard for ARPA Internet Text Messages
        !          1339: 
        !          1340: 
        !          1341:         expansion or transformation, the receiving host  may  wish  to
        !          1342:         record  the original specification, using the "for" parameter.
        !          1343:         For example, when a copy of mail is sent to the  member  of  a
        !          1344:         distribution  list,  this  parameter may be used to record the
        !          1345:         original address that was used to specify the list.
        !          1346: 
        !          1347:      4.4.  ORIGINATOR FIELDS
        !          1348: 
        !          1349:           The standard allows only a subset of the combinations possi-
        !          1350:      ble  with the From, Sender, Reply-To, Resent-From, Resent-Sender,
        !          1351:      and Resent-Reply-To fields.  The limitation is intentional.
        !          1352: 
        !          1353:      4.4.1.  FROM / RESENT-FROM
        !          1354: 
        !          1355:         This field contains the identity of the person(s)  who  wished
        !          1356:         this  message to be sent.  The message-creation process should
        !          1357:         default this field  to  be  a  single,  authenticated  machine
        !          1358:         address,  indicating  the  AGENT  (person,  system or process)
        !          1359:         entering the message.  If this is not done, the "Sender" field
        !          1360:         MUST  be  present.  If the "From" field IS defaulted this way,
        !          1361:         the "Sender" field is  optional  and  is  redundant  with  the
        !          1362:         "From"  field.   In  all  cases, addresses in the "From" field
        !          1363:         must be machine-usable (addr-specs) and may not contain  named
        !          1364:         lists (groups).
        !          1365: 
        !          1366:      4.4.2.  SENDER / RESENT-SENDER
        !          1367: 
        !          1368:         This field contains the authenticated identity  of  the  AGENT
        !          1369:         (person,  system  or  process)  that sends the message.  It is
        !          1370:         intended for use when the sender is not the author of the mes-
        !          1371:         sage,  or  to  indicate  who among a group of authors actually
        !          1372:         sent the message.  If the contents of the "Sender" field would
        !          1373:         be  completely  redundant  with  the  "From"  field,  then the
        !          1374:         "Sender" field need not be present and its use is  discouraged
        !          1375:         (though  still legal).  In particular, the "Sender" field MUST
        !          1376:         be present if it is NOT the same as the "From" Field.
        !          1377: 
        !          1378:         The Sender mailbox  specification  includes  a  word  sequence
        !          1379:         which  must correspond to a specific agent (i.e., a human user
        !          1380:         or a computer program) rather than a standard  address.   This
        !          1381:         indicates  the  expectation  that  the field will identify the
        !          1382:         single AGENT (person,  system,  or  process)  responsible  for
        !          1383:         sending  the mail and not simply include the name of a mailbox
        !          1384:         from which the mail was sent.  For example in the  case  of  a
        !          1385:         shared login name, the name, by itself, would not be adequate.
        !          1386:         The local-part address unit, which refers to  this  agent,  is
        !          1387:         expected to be a computer system term, and not (for example) a
        !          1388:         generalized person reference which can  be  used  outside  the
        !          1389:         network text message context.
        !          1390: 
        !          1391: 
        !          1392:      August 13, 1982              - 21 -                      RFC #822
        !          1393: 
        !          1394: 
        !          1395:  
        !          1396:      Standard for ARPA Internet Text Messages
        !          1397: 
        !          1398: 
        !          1399:         Since the critical function served by the  "Sender"  field  is
        !          1400:         identification  of  the agent responsible for sending mail and
        !          1401:         since computer programs cannot be held accountable  for  their
        !          1402:         behavior, it is strongly recommended that when a computer pro-
        !          1403:         gram generates a message, the HUMAN  who  is  responsible  for
        !          1404:         that program be referenced as part of the "Sender" field mail-
        !          1405:         box specification.
        !          1406: 
        !          1407:      4.4.3.  REPLY-TO / RESENT-REPLY-TO
        !          1408: 
        !          1409:         This field provides a general  mechanism  for  indicating  any
        !          1410:         mailbox(es)  to which responses are to be sent.  Three typical
        !          1411:         uses for this feature can  be  distinguished.   In  the  first
        !          1412:         case,  the  author(s) may not have regular machine-based mail-
        !          1413:         boxes and therefore wish(es) to indicate an alternate  machine
        !          1414:         address.   In  the  second case, an author may wish additional
        !          1415:         persons to be made aware of, or responsible for,  replies.   A
        !          1416:         somewhat  different  use  may be of some help to "text message
        !          1417:         teleconferencing" groups equipped with automatic  distribution
        !          1418:         services:   include the address of that service in the "Reply-
        !          1419:         To" field of all messages  submitted  to  the  teleconference;
        !          1420:         then  participants  can  "reply"  to conference submissions to
        !          1421:         guarantee the correct distribution of any submission of  their
        !          1422:         own.
        !          1423: 
        !          1424:         Note:  The "Return-Path" field is added by the mail  transport
        !          1425:                service,  at the time of final deliver.  It is intended
        !          1426:                to identify a path back to the orginator  of  the  mes-
        !          1427:                sage.   The  "Reply-To"  field  is added by the message
        !          1428:                originator and is intended to direct replies.
        !          1429: 
        !          1430:      4.4.4.  AUTOMATIC USE OF FROM / SENDER / REPLY-TO
        !          1431: 
        !          1432:         For systems which automatically  generate  address  lists  for
        !          1433:         replies to messages, the following recommendations are made:
        !          1434: 
        !          1435:             o   The "Sender" field mailbox should be sent  notices  of
        !          1436:                 any  problems in transport or delivery of the original
        !          1437:                 messages.  If there is no  "Sender"  field,  then  the
        !          1438:                 "From" field mailbox should be used.
        !          1439: 
        !          1440:             o   The  "Sender"  field  mailbox  should  NEVER  be  used
        !          1441:                 automatically, in a recipient's reply message.
        !          1442: 
        !          1443:             o   If the "Reply-To" field exists, then the reply  should
        !          1444:                 go to the addresses indicated in that field and not to
        !          1445:                 the address(es) indicated in the "From" field.
        !          1446: 
        !          1447: 
        !          1448: 
        !          1449: 
        !          1450:      August 13, 1982              - 22 -                      RFC #822
        !          1451: 
        !          1452: 
        !          1453:  
        !          1454:      Standard for ARPA Internet Text Messages
        !          1455: 
        !          1456: 
        !          1457:             o   If there is a "From" field, but no  "Reply-To"  field,
        !          1458:                 the  reply should be sent to the address(es) indicated
        !          1459:                 in the "From" field.
        !          1460: 
        !          1461:         Sometimes, a recipient may actually wish to  communicate  with
        !          1462:         the  person  that  initiated  the  message  transfer.  In such
        !          1463:         cases, it is reasonable to use the "Sender" address.
        !          1464: 
        !          1465:         This recommendation is intended  only  for  automated  use  of
        !          1466:         originator-fields  and is not intended to suggest that replies
        !          1467:         may not also be sent to other recipients of messages.   It  is
        !          1468:         up  to  the  respective  mail-handling programs to decide what
        !          1469:         additional facilities will be provided.
        !          1470: 
        !          1471:         Examples are provided in Appendix A.
        !          1472: 
        !          1473:      4.5.  RECEIVER FIELDS
        !          1474: 
        !          1475:      4.5.1.  TO / RESENT-TO
        !          1476: 
        !          1477:         This field contains the identity of the primary recipients  of
        !          1478:         the message.
        !          1479: 
        !          1480:      4.5.2.  CC / RESENT-CC
        !          1481: 
        !          1482:         This field contains the identity of  the  secondary  (informa-
        !          1483:         tional) recipients of the message.
        !          1484: 
        !          1485:      4.5.3.  BCC / RESENT-BCC
        !          1486: 
        !          1487:         This field contains the identity of additional  recipients  of
        !          1488:         the  message.   The contents of this field are not included in
        !          1489:         copies of the message sent to the primary and secondary  reci-
        !          1490:         pients.   Some  systems  may choose to include the text of the
        !          1491:         "Bcc" field only in the author(s)'s  copy,  while  others  may
        !          1492:         also include it in the text sent to all those indicated in the
        !          1493:         "Bcc" list.
        !          1494: 
        !          1495:      4.6.  REFERENCE FIELDS
        !          1496: 
        !          1497:      4.6.1.  MESSAGE-ID / RESENT-MESSAGE-ID
        !          1498: 
        !          1499:              This field contains a unique identifier  (the  local-part
        !          1500:         address  unit)  which  refers to THIS version of THIS message.
        !          1501:         The uniqueness of the message identifier is guaranteed by  the
        !          1502:         host  which  generates  it.  This identifier is intended to be
        !          1503:         machine readable and not necessarily meaningful to humans.   A
        !          1504:         message  identifier pertains to exactly one instantiation of a
        !          1505:         particular message; subsequent revisions to the message should
        !          1506: 
        !          1507: 
        !          1508:      August 13, 1982              - 23 -                      RFC #822
        !          1509: 
        !          1510: 
        !          1511:  
        !          1512:      Standard for ARPA Internet Text Messages
        !          1513: 
        !          1514: 
        !          1515:         each receive new message identifiers.
        !          1516: 
        !          1517:      4.6.2.  IN-REPLY-TO
        !          1518: 
        !          1519:              The contents of this field identify  previous  correspon-
        !          1520:         dence  which this message answers.  Note that if message iden-
        !          1521:         tifiers are used in this  field,  they  must  use  the  msg-id
        !          1522:         specification format.
        !          1523: 
        !          1524:      4.6.3.  REFERENCES
        !          1525: 
        !          1526:              The contents of this field identify other  correspondence
        !          1527:         which  this message references.  Note that if message identif-
        !          1528:         iers are used, they must use the msg-id specification format.
        !          1529: 
        !          1530:      4.6.4.  KEYWORDS
        !          1531: 
        !          1532:              This field contains keywords  or  phrases,  separated  by
        !          1533:         commas.
        !          1534: 
        !          1535:      4.7.  OTHER FIELDS
        !          1536: 
        !          1537:      4.7.1.  SUBJECT
        !          1538: 
        !          1539:              This is intended to provide a summary,  or  indicate  the
        !          1540:         nature, of the message.
        !          1541: 
        !          1542:      4.7.2.  COMMENTS
        !          1543: 
        !          1544:              Permits adding text comments  onto  the  message  without
        !          1545:         disturbing the contents of the message's body.
        !          1546: 
        !          1547:      4.7.3.  ENCRYPTED
        !          1548: 
        !          1549:              Sometimes,  data  encryption  is  used  to  increase  the
        !          1550:         privacy  of  message  contents.   If the body of a message has
        !          1551:         been encrypted, to keep its contents private, the  "Encrypted"
        !          1552:         field  can be used to note the fact and to indicate the nature
        !          1553:         of the encryption.  The first <word> parameter  indicates  the
        !          1554:         software  used  to  encrypt the body, and the second, optional
        !          1555:         <word> is intended to  aid  the  recipient  in  selecting  the
        !          1556:         proper  decryption  key.   This  code word may be viewed as an
        !          1557:         index to a table of keys held by the recipient.
        !          1558: 
        !          1559:         Note:  Unfortunately, headers must contain envelope,  as  well
        !          1560:                as  contents,  information.  Consequently, it is neces-
        !          1561:                sary that they remain unencrypted, so that  mail  tran-
        !          1562:                sport   services   may   access   them.   Since  names,
        !          1563:                addresses, and "Subject"  field  contents  may  contain
        !          1564: 
        !          1565: 
        !          1566:      August 13, 1982              - 24 -                      RFC #822
        !          1567: 
        !          1568: 
        !          1569:  
        !          1570:      Standard for ARPA Internet Text Messages
        !          1571: 
        !          1572: 
        !          1573:                sensitive  information,  this  requirement limits total
        !          1574:                message privacy.
        !          1575: 
        !          1576:              Names of encryption software are registered with the Net-
        !          1577:         work  Information Center, SRI International, Menlo Park, Cali-
        !          1578:         fornia.
        !          1579: 
        !          1580:      4.7.4.  EXTENSION-FIELD
        !          1581: 
        !          1582:              A limited number of common fields have  been  defined  in
        !          1583:         this  document.   As  network mail requirements dictate, addi-
        !          1584:         tional fields may be standardized.   To  provide  user-defined
        !          1585:         fields  with  a  measure  of  safety,  in name selection, such
        !          1586:         extension-fields will never have names  that  begin  with  the
        !          1587:         string "X-".
        !          1588: 
        !          1589:              Names of Extension-fields are registered with the Network
        !          1590:         Information Center, SRI International, Menlo Park, California.
        !          1591: 
        !          1592:      4.7.5.  USER-DEFINED-FIELD
        !          1593: 
        !          1594:              Individual users of network mail are free to  define  and
        !          1595:         use  additional  header  fields.   Such fields must have names
        !          1596:         which are not already used in the current specification or  in
        !          1597:         any definitions of extension-fields, and the overall syntax of
        !          1598:         these user-defined-fields must conform to this specification's
        !          1599:         rules   for   delimiting  and  folding  fields.   Due  to  the
        !          1600:         extension-field  publishing  process,  the  name  of  a  user-
        !          1601:         defined-field may be pre-empted
        !          1602: 
        !          1603:         Note:  The prefatory string "X-" will never  be  used  in  the
        !          1604:                names  of Extension-fields.  This provides user-defined
        !          1605:                fields with a protected set of names.
        !          1606: 
        !          1607: 
        !          1608: 
        !          1609: 
        !          1610: 
        !          1611: 
        !          1612: 
        !          1613: 
        !          1614: 
        !          1615: 
        !          1616: 
        !          1617: 
        !          1618: 
        !          1619: 
        !          1620: 
        !          1621: 
        !          1622: 
        !          1623: 
        !          1624:      August 13, 1982              - 25 -                      RFC #822
        !          1625: 
        !          1626: 
        !          1627:  
        !          1628:      Standard for ARPA Internet Text Messages
        !          1629: 
        !          1630: 
        !          1631:      5.  DATE AND TIME SPECIFICATION
        !          1632: 
        !          1633:      5.1.  SYNTAX
        !          1634: 
        !          1635:      date-time   =  [ day "," ] date time        ; dd mm yy
        !          1636:                                                  ;  hh:mm:ss zzz
        !          1637: 
        !          1638:      day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"
        !          1639:                  /  "Fri"  / "Sat" /  "Sun"
        !          1640: 
        !          1641:      date        =  1*2DIGIT month 2DIGIT        ; day month year
        !          1642:                                                  ;  e.g. 20 Jun 82
        !          1643: 
        !          1644:      month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"
        !          1645:                  /  "May"  /  "Jun" /  "Jul"  /  "Aug"
        !          1646:                  /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"
        !          1647: 
        !          1648:      time        =  hour zone                    ; ANSI and Military
        !          1649: 
        !          1650:      hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
        !          1651:                                                  ; 00:00:00 - 23:59:59
        !          1652: 
        !          1653:      zone        =  "UT"  / "GMT"                ; Universal Time
        !          1654:                                                  ; North American : UT
        !          1655:                  /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4
        !          1656:                  /  "CST" / "CDT"                ;  Central:  - 6/ - 5
        !          1657:                  /  "MST" / "MDT"                ;  Mountain: - 7/ - 6
        !          1658:                  /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7
        !          1659:                  /  1ALPHA                       ; Military: Z = UT;
        !          1660:                                                  ;  A:-1; (J not used)
        !          1661:                                                  ;  M:-12; N:+1; Y:+12
        !          1662:                  / ( ("+" / "-") 4DIGIT )        ; Local differential
        !          1663:                                                  ;  hours+min. (HHMM)
        !          1664: 
        !          1665:      5.2.  SEMANTICS
        !          1666: 
        !          1667:           If included, day-of-week must be the day implied by the date
        !          1668:      specification.
        !          1669: 
        !          1670:           Time zone may be indicated in several ways.  "UT" is Univer-
        !          1671:      sal  Time  (formerly called "Greenwich Mean Time"); "GMT" is per-
        !          1672:      mitted as a reference to Universal Time.  The  military  standard
        !          1673:      uses  a  single  character for each zone.  "Z" is Universal Time.
        !          1674:      "A" indicates one hour earlier, and "M" indicates 12  hours  ear-
        !          1675:      lier;  "N"  is  one  hour  later, and "Y" is 12 hours later.  The
        !          1676:      letter "J" is not used.  The other remaining two forms are  taken
        !          1677:      from ANSI standard X3.51-1975.  One allows explicit indication of
        !          1678:      the amount of offset from UT; the other uses  common  3-character
        !          1679:      strings for indicating time zones in North America.
        !          1680: 
        !          1681: 
        !          1682:      August 13, 1982              - 26 -                      RFC #822
        !          1683: 
        !          1684: 
        !          1685:  
        !          1686:      Standard for ARPA Internet Text Messages
        !          1687: 
        !          1688: 
        !          1689:      6.  ADDRESS SPECIFICATION
        !          1690: 
        !          1691:      6.1.  SYNTAX
        !          1692: 
        !          1693:      address     =  mailbox                      ; one addressee
        !          1694:                  /  group                        ; named list
        !          1695: 
        !          1696:      group       =  phrase ":" [#mailbox] ";"
        !          1697: 
        !          1698:      mailbox     =  addr-spec                    ; simple address
        !          1699:                  /  phrase route-addr            ; name & addr-spec
        !          1700: 
        !          1701:      route-addr  =  "<" [route] addr-spec ">"
        !          1702: 
        !          1703:      route       =  1#("@" domain) ":"           ; path-relative
        !          1704: 
        !          1705:      addr-spec   =  local-part "@" domain        ; global address
        !          1706: 
        !          1707:      local-part  =  word *("." word)             ; uninterpreted
        !          1708:                                                  ; case-preserved
        !          1709: 
        !          1710:      domain      =  sub-domain *("." sub-domain)
        !          1711: 
        !          1712:      sub-domain  =  domain-ref / domain-literal
        !          1713: 
        !          1714:      domain-ref  =  atom                         ; symbolic reference
        !          1715: 
        !          1716:      6.2.  SEMANTICS
        !          1717: 
        !          1718:           A mailbox receives mail.  It is a  conceptual  entity  which
        !          1719:      does  not necessarily pertain to file storage.  For example, some
        !          1720:      sites may choose to print mail on their line printer and  deliver
        !          1721:      the output to the addressee's desk.
        !          1722: 
        !          1723:           A mailbox specification comprises a person, system  or  pro-
        !          1724:      cess name reference, a domain-dependent string, and a name-domain
        !          1725:      reference.  The name reference is optional and is usually used to
        !          1726:      indicate  the  human name of a recipient.  The name-domain refer-
        !          1727:      ence specifies a sequence of sub-domains.   The  domain-dependent
        !          1728:      string is uninterpreted, except by the final sub-domain; the rest
        !          1729:      of the mail service merely transmits it as a literal string.
        !          1730: 
        !          1731:      6.2.1.  DOMAINS
        !          1732: 
        !          1733:         A name-domain is a set of registered (mail)  names.   A  name-
        !          1734:         domain  specification  resolves  to  a subordinate name-domain
        !          1735:         specification  or  to  a  terminal  domain-dependent   string.
        !          1736:         Hence,  domain  specification  is  extensible,  permitting any
        !          1737:         number of registration levels.
        !          1738: 
        !          1739: 
        !          1740:      August 13, 1982              - 27 -                      RFC #822
        !          1741: 
        !          1742: 
        !          1743:  
        !          1744:      Standard for ARPA Internet Text Messages
        !          1745: 
        !          1746: 
        !          1747:         Name-domains model a global, logical, hierarchical  addressing
        !          1748:         scheme.   The  model is logical, in that an address specifica-
        !          1749:         tion is related to name registration and  is  not  necessarily
        !          1750:         tied  to  transmission  path.   The  model's  hierarchy  is  a
        !          1751:         directed graph, called an in-tree, such that there is a single
        !          1752:         path  from  the root of the tree to any node in the hierarchy.
        !          1753:         If more than one path actually exists, they are considered  to
        !          1754:         be different addresses.
        !          1755: 
        !          1756:         The root node is common to all addresses; consequently, it  is
        !          1757:         not  referenced.   Its  children  constitute "top-level" name-
        !          1758:         domains.  Usually, a service has access to its own full domain
        !          1759:         specification and to the names of all top-level name-domains.
        !          1760: 
        !          1761:         The "top" of the domain addressing hierarchy -- a child of the
        !          1762:         root  --  is  indicated  by  the right-most field, in a domain
        !          1763:         specification.  Its child is specified to the left, its  child
        !          1764:         to the left, and so on.
        !          1765: 
        !          1766:         Some groups provide formal registration services;  these  con-
        !          1767:         stitute   name-domains   that  are  independent  logically  of
        !          1768:         specific machines.  In addition, networks and machines  impli-
        !          1769:         citly  compose name-domains, since their membership usually is
        !          1770:         registered in name tables.
        !          1771: 
        !          1772:         In the case of formal registration, an organization implements
        !          1773:         a  (distributed)  data base which provides an address-to-route
        !          1774:         mapping service for addresses of the form:
        !          1775: 
        !          1776:                          [email protected]
        !          1777: 
        !          1778:         Note that "organization" is a logical  entity,  separate  from
        !          1779:         any particular communication network.
        !          1780: 
        !          1781:         A mechanism for accessing "organization" is universally avail-
        !          1782:         able.   That mechanism, in turn, seeks an instantiation of the
        !          1783:         registry; its location is not indicated in the address specif-
        !          1784:         ication.   It  is assumed that the system which operates under
        !          1785:         the name "organization" knows how to find a subordinate regis-
        !          1786:         try.  The registry will then use the "person" string to deter-
        !          1787:         mine where to send the mail specification.
        !          1788: 
        !          1789:         The latter,  network-oriented  case  permits  simple,  direct,
        !          1790:         attachment-related address specification, such as:
        !          1791: 
        !          1792:                               [email protected]
        !          1793: 
        !          1794:         Once the network is accessed, it is expected  that  a  message
        !          1795:         will  go  directly  to the host and that the host will resolve
        !          1796: 
        !          1797: 
        !          1798:      August 13, 1982              - 28 -                      RFC #822
        !          1799: 
        !          1800: 
        !          1801:  
        !          1802:      Standard for ARPA Internet Text Messages
        !          1803: 
        !          1804: 
        !          1805:         the user name, placing the message in the user's mailbox.
        !          1806: 
        !          1807:      6.2.2.  ABBREVIATED DOMAIN SPECIFICATION
        !          1808: 
        !          1809:         Since any number of  levels  is  possible  within  the  domain
        !          1810:         hierarchy,  specification  of  a  fully  qualified address can
        !          1811:         become inconvenient.  This standard permits abbreviated domain
        !          1812:         specification, in a special case:
        !          1813: 
        !          1814:             For the address of  the  sender,  call  the  left-most
        !          1815:             sub-domain  Level  N.   In a header address, if all of
        !          1816:             the sub-domains above (i.e., to the right of) Level  N
        !          1817:             are  the same as those of the sender, then they do not
        !          1818:             have to appear in the specification.   Otherwise,  the
        !          1819:             address must be fully qualified.
        !          1820: 
        !          1821:             This feature is subject  to  approval  by  local  sub-
        !          1822:             domains.   Individual  sub-domains  may  require their
        !          1823:             member systems, which originate mail, to provide  full
        !          1824:             domain  specification only.  When permitted, abbrevia-
        !          1825:             tions may be present  only  while  the  message  stays
        !          1826:             within the sub-domain of the sender.
        !          1827: 
        !          1828:             Use of this mechanism requires the sender's sub-domain
        !          1829:             to reserve the names of all top-level domains, so that
        !          1830:             full specifications can be distinguished from abbrevi-
        !          1831:             ated specifications.
        !          1832: 
        !          1833:         For example, if a sender's address is:
        !          1834: 
        !          1835:                  [email protected]
        !          1836: 
        !          1837:         and one recipient's address is:
        !          1838: 
        !          1839:                 [email protected]
        !          1840: 
        !          1841:         and another's is:
        !          1842: 
        !          1843:                 [email protected]
        !          1844: 
        !          1845:         then ".registry-1.organization-X" need not be specified in the
        !          1846:         the  message,  but  "registry-C.registry-2"  DOES  have  to be
        !          1847:         specified.  That is, the first two addresses may  be  abbrevi-
        !          1848:         ated, but the third address must be fully specified.
        !          1849: 
        !          1850:         When a message crosses a domain boundary, all  addresses  must
        !          1851:         be  specified  in  the  full format, ending with the top-level
        !          1852:         name-domain in the right-most field.  It is the responsibility
        !          1853:         of  mail  forwarding services to ensure that addresses conform
        !          1854: 
        !          1855: 
        !          1856:      August 13, 1982              - 29 -                      RFC #822
        !          1857: 
        !          1858: 
        !          1859:  
        !          1860:      Standard for ARPA Internet Text Messages
        !          1861: 
        !          1862: 
        !          1863:         with this requirement.  In the case of abbreviated  addresses,
        !          1864:         the  relaying  service must make the necessary expansions.  It
        !          1865:         should be noted that it often is difficult for such a  service
        !          1866:         to locate all occurrences of address abbreviations.  For exam-
        !          1867:         ple, it will not be possible to find such abbreviations within
        !          1868:         the  body  of  the  message.   The "Return-Path" field can aid
        !          1869:         recipients in recovering from these errors.
        !          1870: 
        !          1871:         Note:  When passing any portion of an addr-spec onto a process
        !          1872:                which  does  not interpret data according to this stan-
        !          1873:                dard (e.g., mail protocol servers).  There must  be  NO
        !          1874:                LWSP-chars  preceding  or  following the at-sign or any
        !          1875:                delimiting period ("."), such as  shown  in  the  above
        !          1876:                examples,   and   only  ONE  SPACE  between  contiguous
        !          1877:                <word>s.
        !          1878: 
        !          1879:      6.2.3.  DOMAIN TERMS
        !          1880: 
        !          1881:         A domain-ref must be THE official name of a registry, network,
        !          1882:         or  host.   It  is  a  symbolic  reference, within a name sub-
        !          1883:         domain.  At times, it is necessary to bypass standard  mechan-
        !          1884:         isms  for  resolving  such  references,  using  more primitive
        !          1885:         information, such as a network host address  rather  than  its
        !          1886:         associated host name.
        !          1887: 
        !          1888:         To permit such references, this standard provides the  domain-
        !          1889:         literal  construct.   Its contents must conform with the needs
        !          1890:         of the sub-domain in which it is interpreted.
        !          1891: 
        !          1892:         Domain-literals which refer to domains within the ARPA  Inter-
        !          1893:         net  specify  32-bit  Internet addresses, in four 8-bit fields
        !          1894:         noted in decimal, as described in Request for  Comments  #820,
        !          1895:         "Assigned Numbers."  For example:
        !          1896: 
        !          1897:                                  [10.0.3.19]
        !          1898: 
        !          1899:         Note:  THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED.  It
        !          1900:                is  permitted  only  as  a means of bypassing temporary
        !          1901:                system limitations, such as name tables which  are  not
        !          1902:                complete.
        !          1903: 
        !          1904:         The names of "top-level" domains, and  the  names  of  domains
        !          1905:         under  in  the  ARPA Internet, are registered with the Network
        !          1906:         Information Center, SRI International, Menlo Park, California.
        !          1907: 
        !          1908:      6.2.4.  DOMAIN-DEPENDENT LOCAL STRING
        !          1909: 
        !          1910:         The local-part of an  addr-spec  in  a  mailbox  specification
        !          1911:         (i.e.,  the  host's  name for the mailbox) is understood to be
        !          1912: 
        !          1913: 
        !          1914:      August 13, 1982              - 30 -                      RFC #822
        !          1915: 
        !          1916: 
        !          1917:  
        !          1918:      Standard for ARPA Internet Text Messages
        !          1919: 
        !          1920: 
        !          1921:         whatever the receiving mail protocol server allows.  For exam-
        !          1922:         ple,  some systems do not understand mailbox references of the
        !          1923:         form "P. D. Q. Bach", but others do.
        !          1924: 
        !          1925:         This specification treats periods (".") as lexical separators.
        !          1926:         Hence,  their  presence  in  local-parts which are not quoted-
        !          1927:         strings, is detected.   However,  such  occurrences  carry  NO
        !          1928:         semantics.  That is, if a local-part has periods within it, an
        !          1929:         address parser will divide the local-part into several tokens,
        !          1930:         but  the  sequence  of  tokens will be treated as one uninter-
        !          1931:         preted unit.  The sequence  will  be  re-assembled,  when  the
        !          1932:         address is passed outside of the system such as to a mail pro-
        !          1933:         tocol service.
        !          1934: 
        !          1935:         For example, the address:
        !          1936: 
        !          1937:                            [email protected]
        !          1938: 
        !          1939:         is legal and does not require the local-part to be  surrounded
        !          1940:         with  quotation-marks.   (However,  "First  Last" DOES require
        !          1941:         quoting.)  The local-part of the address, when passed  outside
        !          1942:         of  the  mail  system,  within  the  Registry.Org  domain,  is
        !          1943:         "First.Last", again without quotation marks.
        !          1944: 
        !          1945:      6.2.5.  BALANCING LOCAL-PART AND DOMAIN
        !          1946: 
        !          1947:         In some cases, the boundary between local-part and domain  can
        !          1948:         be  flexible.  The local-part may be a simple string, which is
        !          1949:         used for the final determination of the  recipient's  mailbox.
        !          1950:         All  other  levels  of  reference  are, therefore, part of the
        !          1951:         domain.
        !          1952: 
        !          1953:         For some systems, in the case of abbreviated reference to  the
        !          1954:         local  and  subordinate  sub-domains,  it  may  be possible to
        !          1955:         specify only one reference within the domain  part  and  place
        !          1956:         the  other,  subordinate  name-domain  references  within  the
        !          1957:         local-part.  This would appear as:
        !          1958: 
        !          1959:                         mailbox.sub1.sub2@this-domain
        !          1960: 
        !          1961:         Such a specification would be acceptable  to  address  parsers
        !          1962:         which  conform  to  RFC  #733,  but  do not support this newer
        !          1963:         Internet standard.  While contrary to the intent of this stan-
        !          1964:         dard, the form is legal.
        !          1965: 
        !          1966:         Also, some sub-domains have a specification syntax which  does
        !          1967:         not conform to this standard.  For example:
        !          1968: 
        !          1969:                       [email protected]
        !          1970: 
        !          1971: 
        !          1972:      August 13, 1982              - 31 -                      RFC #822
        !          1973: 
        !          1974: 
        !          1975:  
        !          1976:      Standard for ARPA Internet Text Messages
        !          1977: 
        !          1978: 
        !          1979:         uses a different parsing  sequence  for  local-part  than  for
        !          1980:         domain.
        !          1981: 
        !          1982:         Note:  As a rule,  the  domain  specification  should  contain
        !          1983:                fields  which  are  encoded  according to the syntax of
        !          1984:                this standard and which contain  generally-standardized
        !          1985:                information.   The local-part specification should con-
        !          1986:                tain only that portion of the  address  which  deviates
        !          1987:                from the form or intention of the domain field.
        !          1988: 
        !          1989:      6.2.6.  MULTIPLE MAILBOXES
        !          1990: 
        !          1991:         An individual may have several mailboxes and wish  to  receive
        !          1992:         mail  at  whatever  mailbox  is  convenient  for the sender to
        !          1993:         access.  This standard does not provide a means of  specifying
        !          1994:         "any member of" a list of mailboxes.
        !          1995: 
        !          1996:         A set of individuals may wish to receive mail as a single unit
        !          1997:         (i.e.,  a  distribution  list).  The <group> construct permits
        !          1998:         specification of such a list.  Recipient mailboxes are  speci-
        !          1999:         fied  within  the  bracketed  part (":" - ";").  A copy of the
        !          2000:         transmitted message is to be  sent  to  each  mailbox  listed.
        !          2001:         This  standard  does  not  permit  recursive  specification of
        !          2002:         groups within groups.
        !          2003: 
        !          2004:         While a list must be named, it is not required that  the  con-
        !          2005:         tents  of  the  list be included.  In this case, the <address>
        !          2006:         serves only as an indication of group distribution  and  would
        !          2007:         appear in the form:
        !          2008: 
        !          2009:                                     name:;
        !          2010: 
        !          2011:         Some mail  services  may  provide  a  group-list  distribution
        !          2012:         facility,  accepting  a single mailbox reference, expanding it
        !          2013:         to the full distribution list, and relaying the  mail  to  the
        !          2014:         list's  members.   This standard provides no additional syntax
        !          2015:         for indicating such a  service.   Using  the  <group>  address
        !          2016:         alternative,  while listing one mailbox in it, can mean either
        !          2017:         that the mailbox reference will be expanded to a list or  that
        !          2018:         there is a group with one member.
        !          2019: 
        !          2020:      6.2.7.  EXPLICIT PATH SPECIFICATION
        !          2021: 
        !          2022:         At times, a  message  originator  may  wish  to  indicate  the
        !          2023:         transmission  path  that  a  message  should  follow.  This is
        !          2024:         called source routing.  The normal addressing scheme, used  in
        !          2025:         an  addr-spec,  is  carefully separated from such information;
        !          2026:         the <route> portion of a route-addr is provided for such occa-
        !          2027:         sions.  It specifies the sequence of hosts and/or transmission
        !          2028: 
        !          2029: 
        !          2030:      August 13, 1982              - 32 -                      RFC #822
        !          2031: 
        !          2032: 
        !          2033:  
        !          2034:      Standard for ARPA Internet Text Messages
        !          2035: 
        !          2036: 
        !          2037:         services that are  to  be  traversed.   Both  domain-refs  and
        !          2038:         domain-literals may be used.
        !          2039: 
        !          2040:         Note:  The use of source routing is discouraged.   Unless  the
        !          2041:                sender has special need of path restriction, the choice
        !          2042:                of transmission route should be left to the mail  tran-
        !          2043:                sport service.
        !          2044: 
        !          2045:      6.3.  RESERVED ADDRESS
        !          2046: 
        !          2047:           It often is necessary to send mail to a site, without  know-
        !          2048:      ing  any  of its valid addresses.  For example, there may be mail
        !          2049:      system dysfunctions, or a user may wish to find  out  a  person's
        !          2050:      correct address, at that site.
        !          2051: 
        !          2052:           This standard specifies a single, reserved  mailbox  address
        !          2053:      (local-part)  which  is  to  be valid at each site.  Mail sent to
        !          2054:      that address is to be routed to  a  person  responsible  for  the
        !          2055:      site's mail system or to a person with responsibility for general
        !          2056:      site operation.  The name of the reserved local-part address is:
        !          2057: 
        !          2058:                                 Postmaster
        !          2059: 
        !          2060:      so that "Postmaster@domain" is required to be valid.
        !          2061: 
        !          2062:      Note:  This reserved local-part must be  matched  without  sensi-
        !          2063:             tivity to alphabetic case, so that "POSTMASTER", "postmas-
        !          2064:             ter", and even "poStmASteR" is to be accepted.
        !          2065: 
        !          2066: 
        !          2067: 
        !          2068: 
        !          2069: 
        !          2070: 
        !          2071: 
        !          2072: 
        !          2073: 
        !          2074: 
        !          2075: 
        !          2076: 
        !          2077: 
        !          2078: 
        !          2079: 
        !          2080: 
        !          2081: 
        !          2082: 
        !          2083: 
        !          2084: 
        !          2085: 
        !          2086: 
        !          2087: 
        !          2088:      August 13, 1982              - 33 -                      RFC #822
        !          2089: 
        !          2090: 
        !          2091:  
        !          2092:      Standard for ARPA Internet Text Messages
        !          2093: 
        !          2094: 
        !          2095:      7.  BIBLIOGRAPHY
        !          2096: 
        !          2097: 
        !          2098:      ANSI.  "USA Standard Code  for  Information  Interchange,"  X3.4.
        !          2099:         American  National Standards Institute: New York (1968).  Also
        !          2100:         in:  Feinler, E.  and J. Postel, eds., "ARPANET Protocol Hand-
        !          2101:         book", NIC 7104.
        !          2102: 
        !          2103:      ANSI.  "Representations of Universal Time, Local  Time  Differen-
        !          2104:         tials,  and United States Time Zone References for Information
        !          2105:         Interchange," X3.51-1975.  American National Standards  Insti-
        !          2106:         tute:  New York (1975).
        !          2107: 
        !          2108:      Bemer, R.W., "Time and the Computer."  In:  Interface  Age  (Feb.
        !          2109:         1979).
        !          2110: 
        !          2111:      Bennett, C.J.  "JNT Mail Protocol".  Joint Network Team,  Ruther-
        !          2112:         ford and Appleton Laboratory:  Didcot, England.
        !          2113: 
        !          2114:      Bhushan, A.K., Pogran, K.T., Tomlinson,  R.S.,  and  White,  J.E.
        !          2115:         "Standardizing  Network  Mail  Headers,"   ARPANET Request for
        !          2116:         Comments No. 561, Network Information Center  No.  18516;  SRI
        !          2117:         International:  Menlo Park (September 1973).
        !          2118: 
        !          2119:      Birrell, A.D., Levin, R.,  Needham,  R.M.,  and  Schroeder,  M.D.
        !          2120:         "Grapevine:  An Exercise in Distributed Computing," Communica-
        !          2121:         tions of the ACM 25, 4 (April 1982), 260-274.
        !          2122: 
        !          2123:      Crocker,  D.H.,  Vittal,  J.J.,  Pogran,  K.T.,  Henderson,  D.A.
        !          2124:         "Standard  for  the  Format  of  ARPA  Network  Text Message,"
        !          2125:         ARPANET Request for  Comments  No.  733,  Network  Information
        !          2126:         Center  No.  41952.   SRI International:  Menlo Park (November
        !          2127:         1977).
        !          2128: 
        !          2129:      Feinler, E.J. and Postel, J.B.  ARPANET Protocol  Handbook,  Net-
        !          2130:         work  Information  Center  No.  7104   (NTIS AD A003890).  SRI
        !          2131:         International:  Menlo Park (April 1976).
        !          2132: 
        !          2133:      Harary, F.   "Graph  Theory".   Addison-Wesley:   Reading,  Mass.
        !          2134:         (1969).
        !          2135: 
        !          2136:      Levin, R. and Schroeder, M.  "Transport  of  Electronic  Messages
        !          2137:         through  a  Network,"   TeleInformatics  79, pp. 29-33.  North
        !          2138:         Holland (1979).  Also  as  Xerox  Palo  Alto  Research  Center
        !          2139:         Technical Report CSL-79-4.
        !          2140: 
        !          2141:      Myer, T.H. and Henderson, D.A.  "Message Transmission  Protocol,"
        !          2142:         ARPANET  Request  for  Comments,  No. 680, Network Information
        !          2143:         Center No. 32116.  SRI International:  Menlo Park (1975).
        !          2144: 
        !          2145: 
        !          2146:      August 13, 1982              - 34 -                      RFC #822
        !          2147: 
        !          2148: 
        !          2149:  
        !          2150:      Standard for ARPA Internet Text Messages
        !          2151: 
        !          2152: 
        !          2153:      NBS.  "Specification of Message Format for Computer Based Message
        !          2154:         Systems, Recommended Federal Information Processing Standard."
        !          2155:         National  Bureau   of   Standards:    Gaithersburg,   Maryland
        !          2156:         (October 1981).
        !          2157: 
        !          2158:      NIC.  Internet Protocol Transition Workbook.  Network Information
        !          2159:         Center,   SRI-International,  Menlo  Park,  California  (March
        !          2160:         1982).
        !          2161: 
        !          2162:      Oppen, D.C. and Dalal, Y.K.  "The Clearinghouse:  A Decentralized
        !          2163:         Agent  for  Locating  Named  Objects in a Distributed Environ-
        !          2164:         ment," OPD-T8103.  Xerox Office Products Division:  Palo Alto,
        !          2165:         CA. (October 1981).
        !          2166: 
        !          2167:      Postel, J.B.  "Assigned Numbers,"  ARPANET Request for  Comments,
        !          2168:         No. 820.  SRI International:  Menlo Park (August 1982).
        !          2169: 
        !          2170:      Postel, J.B.  "Simple Mail Transfer  Protocol,"  ARPANET  Request
        !          2171:         for Comments, No. 821.  SRI International:  Menlo Park (August
        !          2172:         1982).
        !          2173: 
        !          2174:      Shoch, J.F.  "Internetwork naming, addressing  and  routing,"  in
        !          2175:         Proc. 17th IEEE Computer Society International Conference, pp.
        !          2176:         72-79, Sept. 1978, IEEE Cat. No. 78 CH 1388-8C.
        !          2177: 
        !          2178:      Su, Z. and Postel, J.  "The Domain Naming Convention for Internet
        !          2179:         User  Applications,"  ARPANET  Request  for Comments, No. 819.
        !          2180:         SRI International:  Menlo Park (August 1982).
        !          2181: 
        !          2182: 
        !          2183: 
        !          2184: 
        !          2185: 
        !          2186: 
        !          2187: 
        !          2188: 
        !          2189: 
        !          2190: 
        !          2191: 
        !          2192: 
        !          2193: 
        !          2194: 
        !          2195: 
        !          2196: 
        !          2197: 
        !          2198: 
        !          2199: 
        !          2200: 
        !          2201: 
        !          2202: 
        !          2203: 
        !          2204:      August 13, 1982              - 35 -                      RFC #822
        !          2205: 
        !          2206: 
        !          2207:  
        !          2208:      Standard for ARPA Internet Text Messages
        !          2209: 
        !          2210: 
        !          2211:                                  APPENDIX
        !          2212: 
        !          2213: 
        !          2214:      A.  EXAMPLES
        !          2215: 
        !          2216:      A.1.  ADDRESSES
        !          2217: 
        !          2218:      A.1.1.  Alfred Neuman <Neuman@BBN-TENEXA>
        !          2219: 
        !          2220:      A.1.2.  Neuman@BBN-TENEXA
        !          2221: 
        !          2222:              These two "Alfred Neuman" examples have identical  seman-
        !          2223:         tics, as far as the operation of the local host's mail sending
        !          2224:         (distribution) program (also sometimes  called  its  "mailer")
        !          2225:         and  the remote host's mail protocol server are concerned.  In
        !          2226:         the first example, the  "Alfred  Neuman"  is  ignored  by  the
        !          2227:         mailer,  as "Neuman@BBN-TENEXA" completely specifies the reci-
        !          2228:         pient.  The second example contains  no  superfluous  informa-
        !          2229:         tion,  and,  again,  "Neuman@BBN-TENEXA" is the intended reci-
        !          2230:         pient.
        !          2231: 
        !          2232:         Note:  When the message crosses name-domain  boundaries,  then
        !          2233:                these specifications must be changed, so as to indicate
        !          2234:                the remainder of the hierarchy, starting with  the  top
        !          2235:                level.
        !          2236: 
        !          2237:      A.1.3.  "George, Ted" <[email protected]>
        !          2238: 
        !          2239:              This form might be used to indicate that a single mailbox
        !          2240:         is  shared  by several users.  The quoted string is ignored by
        !          2241:         the originating host's mailer, because  "[email protected]"
        !          2242:         completely specifies the destination mailbox.
        !          2243: 
        !          2244:      A.1.4.  Wilt . (the  Stilt) [email protected]
        !          2245: 
        !          2246:              The "(the  Stilt)" is a comment, which is NOT included in
        !          2247:         the  destination  mailbox  address  handed  to the originating
        !          2248:         system's mailer.  The local-part of the address is the  string
        !          2249:         "Wilt.Chamberlain", with NO space between the first and second
        !          2250:         words.
        !          2251: 
        !          2252:      A.1.5.  Address Lists
        !          2253: 
        !          2254:      Gourmets:  Pompous Person <WhoZiWhatZit@Cordon-Bleu>,
        !          2255:                 [email protected], Galloping Gourmet@
        !          2256:                 ANT.Down-Under (Australian National Television),
        !          2257:                 Cheapie@Discount-Liquors;,
        !          2258:        Cruisers:  Port@Portugal, Jones@SEA;,
        !          2259:          [email protected]
        !          2260: 
        !          2261: 
        !          2262:      August 13, 1982              - 36 -                      RFC #822
        !          2263: 
        !          2264: 
        !          2265:  
        !          2266:      Standard for ARPA Internet Text Messages
        !          2267: 
        !          2268: 
        !          2269:         This group list example points out the use of comments and the
        !          2270:         mixing of addresses and groups.
        !          2271: 
        !          2272:      A.2.  ORIGINATOR ITEMS
        !          2273: 
        !          2274:      A.2.1.  Author-sent
        !          2275: 
        !          2276:              George Jones logs into his host  as  "Jones".   He  sends
        !          2277:         mail himself.
        !          2278: 
        !          2279:             From:  [email protected]
        !          2280: 
        !          2281:         or
        !          2282: 
        !          2283:             From:  George Jones <[email protected]>
        !          2284: 
        !          2285:      A.2.2.  Secretary-sent
        !          2286: 
        !          2287:              George Jones logs in as Jones on his  host.   His  secre-
        !          2288:         tary,  who logs in as Secy sends mail for him.  Replies to the
        !          2289:         mail should go to George.
        !          2290: 
        !          2291:             From:    George Jones <Jones@Group>
        !          2292:             Sender:  Secy@Other-Group
        !          2293: 
        !          2294:      A.2.3.  Secretary-sent, for user of shared directory
        !          2295: 
        !          2296:              George Jones' secretary sends mail  for  George.  Replies
        !          2297:         should go to George.
        !          2298: 
        !          2299:             From:     George Jones<[email protected]>
        !          2300:             Sender:   Secy@Other-Group
        !          2301: 
        !          2302:         Note that there need not be a space between  "Jones"  and  the
        !          2303:         "<",  but  adding a space enhances readability (as is the case
        !          2304:         in other examples.
        !          2305: 
        !          2306:      A.2.4.  Committee activity, with one author
        !          2307: 
        !          2308:              George is a member of a committee.  He wishes to have any
        !          2309:         replies to his message go to all committee members.
        !          2310: 
        !          2311:             From:     George Jones <[email protected]>
        !          2312:             Sender:   Jones@Host
        !          2313:             Reply-To: The Committee: [email protected],
        !          2314:                                      [email protected],
        !          2315:                                      Doe@Somewhere-Else;
        !          2316: 
        !          2317:         Note  that  if  George  had  not  included  himself   in   the
        !          2318: 
        !          2319: 
        !          2320:      August 13, 1982              - 37 -                      RFC #822
        !          2321: 
        !          2322: 
        !          2323:  
        !          2324:      Standard for ARPA Internet Text Messages
        !          2325: 
        !          2326: 
        !          2327:         enumeration  of  The  Committee,  he  would not have gotten an
        !          2328:         implicit reply; the presence of the  "Reply-to"  field  SUPER-
        !          2329:         SEDES the sending of a reply to the person named in the "From"
        !          2330:         field.
        !          2331: 
        !          2332:      A.2.5.  Secretary acting as full agent of author
        !          2333: 
        !          2334:              George Jones asks his secretary  (Secy@Host)  to  send  a
        !          2335:         message for him in his capacity as Group.  He wants his secre-
        !          2336:         tary to handle all replies.
        !          2337: 
        !          2338:             From:     George Jones <Group@Host>
        !          2339:             Sender:   Secy@Host
        !          2340:             Reply-To: Secy@Host
        !          2341: 
        !          2342:      A.2.6.  Agent for user without online mailbox
        !          2343: 
        !          2344:              A friend  of  George's,  Sarah,  is  visiting.   George's
        !          2345:         secretary  sends  some  mail to a friend of Sarah in computer-
        !          2346:         land.  Replies should go to George, whose mailbox is Jones  at
        !          2347:         Registry.
        !          2348: 
        !          2349:             From:     Sarah Friendly <Secy@Registry>
        !          2350:             Sender:   Secy-Name <Secy@Registry>
        !          2351:             Reply-To: Jones@Registry.
        !          2352: 
        !          2353:      A.2.7.  Agent for member of a committee
        !          2354: 
        !          2355:              George's secretary sends out a message which was authored
        !          2356:         jointly by all the members of a committee.  Note that the name
        !          2357:         of the committee cannot be specified, since <group> names  are
        !          2358:         not permitted in the From field.
        !          2359: 
        !          2360:             From:   Jones@Host,
        !          2361:                     Smith@Other-Host,
        !          2362:                     Doe@Somewhere-Else
        !          2363:             Sender: Secy@SHost
        !          2364: 
        !          2365: 
        !          2366: 
        !          2367: 
        !          2368: 
        !          2369: 
        !          2370: 
        !          2371: 
        !          2372: 
        !          2373: 
        !          2374: 
        !          2375: 
        !          2376: 
        !          2377: 
        !          2378:      August 13, 1982              - 38 -                      RFC #822
        !          2379: 
        !          2380: 
        !          2381:  
        !          2382:      Standard for ARPA Internet Text Messages
        !          2383: 
        !          2384: 
        !          2385:      A.3.  COMPLETE HEADERS
        !          2386: 
        !          2387:      A.3.1.  Minimum required
        !          2388: 
        !          2389:      Date:     26 Aug 76 1429 EDT        Date:     26 Aug 76 1429 EDT
        !          2390:      From:     [email protected]   or   From:     [email protected]
        !          2391:      Bcc:                                To:       [email protected]
        !          2392: 
        !          2393:         Note that the "Bcc" field may be empty, while the  "To"  field
        !          2394:         is required to have at least one address.
        !          2395: 
        !          2396:      A.3.2.  Using some of the additional fields
        !          2397: 
        !          2398:      Date:     26 Aug 76 1430 EDT
        !          2399:      From:     George Jones<Group@Host>
        !          2400:      Sender:   Secy@SHOST
        !          2401:      To:       "Al Neuman"@Mad-Host,
        !          2402:                Sam.Irving@Other-Host
        !          2403:      Message-ID:  <some.string@SHOST>
        !          2404: 
        !          2405:      A.3.3.  About as complex as you're going to get
        !          2406: 
        !          2407:      Date     :  27 Aug 76 0932 PDT
        !          2408:      From     :  Ken Davis <[email protected]>
        !          2409:      Subject  :  Re: The Syntax in the RFC
        !          2410:      Sender   :  KSecy@Other-Host
        !          2411:      Reply-To :  [email protected]
        !          2412:      To       :  George Jones <[email protected]>,
        !          2413:                  [email protected]
        !          2414:      cc       :  Important folk:
        !          2415:                    Tom Softwood <[email protected]>,
        !          2416:                    "Sam Irving"@Other-Host;,
        !          2417:                  Standard Distribution:
        !          2418:                    /main/davis/people/standard@Other-Host,
        !          2419:                    "<Jones>standard.dist.3"@Tops-20-Host>;
        !          2420:      Comment  :  Sam is away on business. He asked me to handle
        !          2421:                  his mail for him.  He'll be able to provide  a
        !          2422:                  more  accurate  explanation  when  he  returns
        !          2423:                  next week.
        !          2424:      In-Reply-To: <[email protected]>, George's message
        !          2425:      X-Special-action:  This is a sample of user-defined field-
        !          2426:                  names.  There could also be a field-name
        !          2427:                  "Special-action", but its name might later be
        !          2428:                  preempted
        !          2429:      Message-ID: <4231.629.XYzi-What@Other-Host>
        !          2430: 
        !          2431: 
        !          2432: 
        !          2433: 
        !          2434: 
        !          2435: 
        !          2436:      August 13, 1982              - 39 -                      RFC #822
        !          2437: 
        !          2438: 
        !          2439:  
        !          2440:      Standard for ARPA Internet Text Messages
        !          2441: 
        !          2442: 
        !          2443:      B.  SIMPLE FIELD PARSING
        !          2444: 
        !          2445:           Some mail-reading software systems may wish to perform  only
        !          2446:      minimal  processing,  ignoring  the internal syntax of structured
        !          2447:      field-bodies and treating them the  same  as  unstructured-field-
        !          2448:      bodies.  Such software will need only to distinguish:
        !          2449: 
        !          2450:          o   Header fields from the message body,
        !          2451: 
        !          2452:          o   Beginnings of fields from lines which continue fields,
        !          2453: 
        !          2454:          o   Field-names from field-contents.
        !          2455: 
        !          2456:           The abbreviated set of syntactic rules  which  follows  will
        !          2457:      suffice  for  this  purpose.  It describes a limited view of mes-
        !          2458:      sages and is a subset of the syntactic rules provided in the main
        !          2459:      part of this specification.  One small exception is that the con-
        !          2460:      tents of field-bodies consist only of text:
        !          2461: 
        !          2462:      B.1.  SYNTAX
        !          2463: 
        !          2464: 
        !          2465:      message         =   *field *(CRLF *text)
        !          2466: 
        !          2467:      field           =    field-name ":" [field-body] CRLF
        !          2468: 
        !          2469:      field-name      =  1*<any CHAR, excluding CTLs, SPACE, and ":">
        !          2470: 
        !          2471:      field-body      =   *text [CRLF LWSP-char field-body]
        !          2472: 
        !          2473: 
        !          2474:      B.2.  SEMANTICS
        !          2475: 
        !          2476:           Headers occur before the message body and are terminated  by
        !          2477:      a null line (i.e., two contiguous CRLFs).
        !          2478: 
        !          2479:           A line which continues a header field begins with a SPACE or
        !          2480:      HTAB  character,  while  a  line  beginning a field starts with a
        !          2481:      printable character which is not a colon.
        !          2482: 
        !          2483:           A field-name consists of one or  more  printable  characters
        !          2484:      (excluding  colon,  space, and control-characters).  A field-name
        !          2485:      MUST be contained on one line.  Upper and lower case are not dis-
        !          2486:      tinguished when comparing field-names.
        !          2487: 
        !          2488: 
        !          2489: 
        !          2490: 
        !          2491: 
        !          2492: 
        !          2493: 
        !          2494:      August 13, 1982              - 40 -                      RFC #822
        !          2495: 
        !          2496: 
        !          2497:  
        !          2498:      Standard for ARPA Internet Text Messages
        !          2499: 
        !          2500: 
        !          2501:      C.  DIFFERENCES FROM RFC #733
        !          2502: 
        !          2503:           The following summarizes the differences between this  stan-
        !          2504:      dard  and the one specified in Arpanet Request for Comments #733,
        !          2505:      "Standard for the Format of ARPA  Network  Text  Messages".   The
        !          2506:      differences  are  listed  in the order of their occurrence in the
        !          2507:      current specification.
        !          2508: 
        !          2509:      C.1.  FIELD DEFINITIONS
        !          2510: 
        !          2511:      C.1.1.  FIELD NAMES
        !          2512: 
        !          2513:         These now must be a sequence of  printable  characters.   They
        !          2514:         may not contain any LWSP-chars.
        !          2515: 
        !          2516:      C.2.  LEXICAL TOKENS
        !          2517: 
        !          2518:      C.2.1.  SPECIALS
        !          2519: 
        !          2520:         The characters period ("."), left-square  bracket  ("["),  and
        !          2521:         right-square  bracket ("]") have been added.  For presentation
        !          2522:         purposes, and when passing a specification to  a  system  that
        !          2523:         does  not conform to this standard, periods are to be contigu-
        !          2524:         ous with their surrounding lexical tokens.   No  linear-white-
        !          2525:         space  is  permitted  between them.  The presence of one LWSP-
        !          2526:         char between other tokens is still directed.
        !          2527: 
        !          2528:      C.2.2.  ATOM
        !          2529: 
        !          2530:         Atoms may not contain SPACE.
        !          2531: 
        !          2532:      C.2.3.  SPECIAL TEXT
        !          2533: 
        !          2534:         ctext and qtext have had backslash ("\") added to the list  of
        !          2535:         prohibited characters.
        !          2536: 
        !          2537:      C.2.4.  DOMAINS
        !          2538: 
        !          2539:         The lexical tokens  <domain-literal>  and  <dtext>  have  been
        !          2540:         added.
        !          2541: 
        !          2542:      C.3.  MESSAGE SPECIFICATION
        !          2543: 
        !          2544:      C.3.1.  TRACE
        !          2545: 
        !          2546:         The "Return-path:" and "Received:" fields have been specified.
        !          2547: 
        !          2548: 
        !          2549: 
        !          2550: 
        !          2551: 
        !          2552:      August 13, 1982              - 41 -                      RFC #822
        !          2553: 
        !          2554: 
        !          2555:  
        !          2556:      Standard for ARPA Internet Text Messages
        !          2557: 
        !          2558: 
        !          2559:      C.3.2.  FROM
        !          2560: 
        !          2561:         The "From" field must contain machine-usable addresses  (addr-
        !          2562:         spec).   Multiple  addresses may be specified, but named-lists
        !          2563:         (groups) may not.
        !          2564: 
        !          2565:      C.3.3.  RESENT
        !          2566: 
        !          2567:         The meta-construct of prefacing field names  with  the  string
        !          2568:         "Resent-"  has been added, to indicate that a message has been
        !          2569:         forwarded by an intermediate recipient.
        !          2570: 
        !          2571:      C.3.4.  DESTINATION
        !          2572: 
        !          2573:         A message must contain at least one destination address field.
        !          2574:         "To" and "CC" are required to contain at least one address.
        !          2575: 
        !          2576:      C.3.5.  IN-REPLY-TO
        !          2577: 
        !          2578:         The field-body is no longer a comma-separated list, although a
        !          2579:         sequence is still permitted.
        !          2580: 
        !          2581:      C.3.6.  REFERENCE
        !          2582: 
        !          2583:         The field-body is no longer a comma-separated list, although a
        !          2584:         sequence is still permitted.
        !          2585: 
        !          2586:      C.3.7.  ENCRYPTED
        !          2587: 
        !          2588:         A field has been specified that permits  senders  to  indicate
        !          2589:         that the body of a message has been encrypted.
        !          2590: 
        !          2591:      C.3.8.  EXTENSION-FIELD
        !          2592: 
        !          2593:         Extension fields are prohibited from beginning with the  char-
        !          2594:         acters "X-".
        !          2595: 
        !          2596:      C.4.  DATE AND TIME SPECIFICATION
        !          2597: 
        !          2598:      C.4.1.  SIMPLIFICATION
        !          2599: 
        !          2600:         Fewer optional forms are permitted  and  the  list  of  three-
        !          2601:         letter time zones has been shortened.
        !          2602: 
        !          2603:      C.5.  ADDRESS SPECIFICATION
        !          2604: 
        !          2605: 
        !          2606: 
        !          2607: 
        !          2608: 
        !          2609: 
        !          2610:      August 13, 1982              - 42 -                      RFC #822
        !          2611: 
        !          2612: 
        !          2613:  
        !          2614:      Standard for ARPA Internet Text Messages
        !          2615: 
        !          2616: 
        !          2617:      C.5.1.  ADDRESS
        !          2618: 
        !          2619:         The use of quoted-string, and the ":"-atom-":" construct, have
        !          2620:         been  removed.   An  address  now  is  either a single mailbox
        !          2621:         reference or is a named list of addresses.  The  latter  indi-
        !          2622:         cates a group distribution.
        !          2623: 
        !          2624:      C.5.2.  GROUPS
        !          2625: 
        !          2626:         Group lists are now required to to have a name.   Group  lists
        !          2627:         may not be nested.
        !          2628: 
        !          2629:      C.5.3.  MAILBOX
        !          2630: 
        !          2631:         A mailbox specification  may  indicate  a  person's  name,  as
        !          2632:         before.   Such  a  named  list  no longer may specify multiple
        !          2633:         mailboxes and may not be nested.
        !          2634: 
        !          2635:      C.5.4.  ROUTE ADDRESSING
        !          2636: 
        !          2637:         Addresses now are taken to be absolute, global specifications,
        !          2638:         independent  of transmission paths.  The <route> construct has
        !          2639:         been provided, to permit explicit specification  of  transmis-
        !          2640:         sion  path.   RFC  #733's  use  of multiple at-signs ("@") was
        !          2641:         intended as a general syntax  for  indicating  routing  and/or
        !          2642:         hierarchical addressing.  The current standard separates these
        !          2643:         specifications and only one at-sign is permitted.
        !          2644: 
        !          2645:      C.5.5.  AT-SIGN
        !          2646: 
        !          2647:         The string " at " no longer is used as an  address  delimiter.
        !          2648:         Only at-sign ("@") serves the function.
        !          2649: 
        !          2650:      C.5.6.  DOMAINS
        !          2651: 
        !          2652:         Hierarchical, logical name-domains have been added.
        !          2653: 
        !          2654:      C.6.  RESERVED ADDRESS
        !          2655: 
        !          2656:      The local-part "Postmaster" has been reserved, so that users  can
        !          2657:      be guaranteed at least one valid address at a site.
        !          2658: 
        !          2659: 
        !          2660: 
        !          2661: 
        !          2662: 
        !          2663: 
        !          2664: 
        !          2665: 
        !          2666: 
        !          2667: 
        !          2668:      August 13, 1982              - 43 -                      RFC #822
        !          2669: 
        !          2670: 
        !          2671:  
        !          2672:      Standard for ARPA Internet Text Messages
        !          2673: 
        !          2674: 
        !          2675:      D.  ALPHABETICAL LISTING OF SYNTAX RULES
        !          2676: 
        !          2677:      address     =  mailbox                      ; one addressee
        !          2678:                  /  group                        ; named list
        !          2679:      addr-spec   =  local-part "@" domain        ; global address
        !          2680:      ALPHA       =  <any ASCII alphabetic character>
        !          2681:                                                  ; (101-132, 65.- 90.)
        !          2682:                                                  ; (141-172, 97.-122.)
        !          2683:      atom        =  1*<any CHAR except specials, SPACE and CTLs>
        !          2684:      authentic   =   "From"       ":"   mailbox  ; Single author
        !          2685:                  / ( "Sender"     ":"   mailbox  ; Actual submittor
        !          2686:                      "From"       ":" 1#mailbox) ; Multiple authors
        !          2687:                                                  ;  or not sender
        !          2688:      CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
        !          2689:      comment     =  "(" *(ctext / quoted-pair / comment) ")"
        !          2690:      CR          =  <ASCII CR, carriage return>  ; (     15,      13.)
        !          2691:      CRLF        =  CR LF
        !          2692:      ctext       =  <any CHAR excluding "(",     ; => may be folded
        !          2693:                      ")", "\" & CR, & including
        !          2694:                      linear-white-space>
        !          2695:      CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
        !          2696:                      character and DEL>          ; (    177,     127.)
        !          2697:      date        =  1*2DIGIT month 2DIGIT        ; day month year
        !          2698:                                                  ;  e.g. 20 Jun 82
        !          2699:      dates       =   orig-date                   ; Original
        !          2700:                    [ resent-date ]               ; Forwarded
        !          2701:      date-time   =  [ day "," ] date time        ; dd mm yy
        !          2702:                                                  ;  hh:mm:ss zzz
        !          2703:      day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"
        !          2704:                  /  "Fri"  / "Sat" /  "Sun"
        !          2705:      delimiters  =  specials / linear-white-space / comment
        !          2706:      destination =  "To"          ":" 1#address  ; Primary
        !          2707:                  /  "Resent-To"   ":" 1#address
        !          2708:                  /  "cc"          ":" 1#address  ; Secondary
        !          2709:                  /  "Resent-cc"   ":" 1#address
        !          2710:                  /  "bcc"         ":"  #address  ; Blind carbon
        !          2711:                  /  "Resent-bcc"  ":"  #address
        !          2712:      DIGIT       =  <any ASCII decimal digit>    ; ( 60- 71, 48.- 57.)
        !          2713:      domain      =  sub-domain *("." sub-domain)
        !          2714:      domain-literal =  "[" *(dtext / quoted-pair) "]"
        !          2715:      domain-ref  =  atom                         ; symbolic reference
        !          2716:      dtext       =  <any CHAR excluding "[",     ; => may be folded
        !          2717:                      "]", "\" & CR, & including
        !          2718:                      linear-white-space>
        !          2719:      extension-field =
        !          2720:                    <Any field which is defined in a document
        !          2721:                     published as a formal extension to this
        !          2722:                     specification; none will have names beginning
        !          2723:                     with the string "X-">
        !          2724: 
        !          2725: 
        !          2726:      August 13, 1982              - 44 -                      RFC #822
        !          2727: 
        !          2728: 
        !          2729:  
        !          2730:      Standard for ARPA Internet Text Messages
        !          2731: 
        !          2732: 
        !          2733:      field       =  field-name ":" [ field-body ] CRLF
        !          2734:      fields      =    dates                      ; Creation time,
        !          2735:                       source                     ;  author id & one
        !          2736:                     1*destination                ;  address required
        !          2737:                      *optional-field             ;  others optional
        !          2738:      field-body  =  field-body-contents
        !          2739:                     [CRLF LWSP-char field-body]
        !          2740:      field-body-contents =
        !          2741:                    <the ASCII characters making up the field-body, as
        !          2742:                     defined in the following sections, and consisting
        !          2743:                     of combinations of atom, quoted-string, and
        !          2744:                     specials tokens, or else consisting of texts>
        !          2745:      field-name  =  1*<any CHAR, excluding CTLs, SPACE, and ":">
        !          2746:      group       =  phrase ":" [#mailbox] ";"
        !          2747:      hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
        !          2748:                                                  ; 00:00:00 - 23:59:59
        !          2749:      HTAB        =  <ASCII HT, horizontal-tab>   ; (     11,       9.)
        !          2750:      LF          =  <ASCII LF, linefeed>         ; (     12,      10.)
        !          2751:      linear-white-space =  1*([CRLF] LWSP-char)  ; semantics = SPACE
        !          2752:                                                  ; CRLF => folding
        !          2753:      local-part  =  word *("." word)             ; uninterpreted
        !          2754:                                                  ; case-preserved
        !          2755:      LWSP-char   =  SPACE / HTAB                 ; semantics = SPACE
        !          2756:      mailbox     =  addr-spec                    ; simple address
        !          2757:                  /  phrase route-addr            ; name & addr-spec
        !          2758:      message     =  fields *( CRLF *text )       ; Everything after
        !          2759:                                                  ;  first null line
        !          2760:                                                  ;  is message body
        !          2761:      month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"
        !          2762:                  /  "May"  /  "Jun" /  "Jul"  /  "Aug"
        !          2763:                  /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"
        !          2764:      msg-id      =  "<" addr-spec ">"            ; Unique message id
        !          2765:      optional-field =
        !          2766:                  /  "Message-ID"        ":"   msg-id
        !          2767:                  /  "Resent-Message-ID" ":"   msg-id
        !          2768:                  /  "In-Reply-To"       ":"  *(phrase / msg-id)
        !          2769:                  /  "References"        ":"  *(phrase / msg-id)
        !          2770:                  /  "Keywords"          ":"  #phrase
        !          2771:                  /  "Subject"           ":"  *text
        !          2772:                  /  "Comments"          ":"  *text
        !          2773:                  /  "Encrypted"         ":" 1#2word
        !          2774:                  /  extension-field              ; To be defined
        !          2775:                  /  user-defined-field           ; May be pre-empted
        !          2776:      orig-date   =  "Date"        ":"   date-time
        !          2777:      originator  =   authentic                   ; authenticated addr
        !          2778:                    [ "Reply-To"   ":" 1#address] )
        !          2779:      phrase      =  1*word                       ; Sequence of words
        !          2780: 
        !          2781: 
        !          2782: 
        !          2783: 
        !          2784:      August 13, 1982              - 45 -                      RFC #822
        !          2785: 
        !          2786: 
        !          2787:  
        !          2788:      Standard for ARPA Internet Text Messages
        !          2789: 
        !          2790: 
        !          2791:      qtext       =  <any CHAR excepting <">,     ; => may be folded
        !          2792:                      "\" & CR, and including
        !          2793:                      linear-white-space>
        !          2794:      quoted-pair =  "\" CHAR                     ; may quote any char
        !          2795:      quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
        !          2796:                                                  ;   quoted chars.
        !          2797:      received    =  "Received"    ":"            ; one per relay
        !          2798:                        ["from" domain]           ; sending host
        !          2799:                        ["by"   domain]           ; receiving host
        !          2800:                        ["via"  atom]             ; physical path
        !          2801:                       *("with" atom)             ; link/mail protocol
        !          2802:                        ["id"   msg-id]           ; receiver msg id
        !          2803:                        ["for"  addr-spec]        ; initial form
        !          2804:                         ";"    date-time         ; time received
        !          2805: 
        !          2806:      resent      =   resent-authentic
        !          2807:                    [ "Resent-Reply-To"  ":" 1#address] )
        !          2808:      resent-authentic =
        !          2809:                  =   "Resent-From"      ":"   mailbox
        !          2810:                  / ( "Resent-Sender"    ":"   mailbox
        !          2811:                      "Resent-From"      ":" 1#mailbox  )
        !          2812:      resent-date =  "Resent-Date" ":"   date-time
        !          2813:      return      =  "Return-path" ":" route-addr ; return address
        !          2814:      route       =  1#("@" domain) ":"           ; path-relative
        !          2815:      route-addr  =  "<" [route] addr-spec ">"
        !          2816:      source      = [  trace ]                    ; net traversals
        !          2817:                       originator                 ; original mail
        !          2818:                    [  resent ]                   ; forwarded
        !          2819:      SPACE       =  <ASCII SP, space>            ; (     40,      32.)
        !          2820:      specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
        !          2821:                  /  "," / ";" / ":" / "\" / <">  ;  string, to use
        !          2822:                  /  "." / "[" / "]"              ;  within a word.
        !          2823:      sub-domain  =  domain-ref / domain-literal
        !          2824:      text        =  <any CHAR, including bare    ; => atoms, specials,
        !          2825:                      CR & bare LF, but NOT       ;  comments and
        !          2826:                      including CRLF>             ;  quoted-strings are
        !          2827:                                                  ;  NOT recognized.
        !          2828:      time        =  hour zone                    ; ANSI and Military
        !          2829:      trace       =    return                     ; path to sender
        !          2830:                     1*received                   ; receipt tags
        !          2831:      user-defined-field =
        !          2832:                    <Any field which has not been defined
        !          2833:                     in this specification or published as an
        !          2834:                     extension to this specification; names for
        !          2835:                     such fields must be unique and may be
        !          2836:                     pre-empted by published extensions>
        !          2837:      word        =  atom / quoted-string
        !          2838: 
        !          2839: 
        !          2840: 
        !          2841: 
        !          2842:      August 13, 1982              - 46 -                      RFC #822
        !          2843: 
        !          2844: 
        !          2845:  
        !          2846:      Standard for ARPA Internet Text Messages
        !          2847: 
        !          2848: 
        !          2849:      zone        =  "UT"  / "GMT"                ; Universal Time
        !          2850:                                                  ; North American : UT
        !          2851:                  /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4
        !          2852:                  /  "CST" / "CDT"                ;  Central:  - 6/ - 5
        !          2853:                  /  "MST" / "MDT"                ;  Mountain: - 7/ - 6
        !          2854:                  /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7
        !          2855:                  /  1ALPHA                       ; Military: Z = UT;
        !          2856:      <">         =  <ASCII quote mark>           ; (     42,      34.)
        !          2857: 
        !          2858: 
        !          2859: 
        !          2860: 
        !          2861: 
        !          2862: 
        !          2863: 
        !          2864: 
        !          2865: 
        !          2866: 
        !          2867: 
        !          2868: 
        !          2869: 
        !          2870: 
        !          2871: 
        !          2872: 
        !          2873: 
        !          2874: 
        !          2875: 
        !          2876: 
        !          2877: 
        !          2878: 
        !          2879: 
        !          2880: 
        !          2881: 
        !          2882: 
        !          2883: 
        !          2884: 
        !          2885: 
        !          2886: 
        !          2887: 
        !          2888: 
        !          2889: 
        !          2890: 
        !          2891: 
        !          2892: 
        !          2893: 
        !          2894: 
        !          2895: 
        !          2896: 
        !          2897: 
        !          2898: 
        !          2899: 
        !          2900:      August 13, 1982              - 47 -                      RFC #822
        !          2901: 

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