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1.1 ! root 1: .TL ! 2: MMDFII: ! 3: A Technical Review ! 4: .AU ! 5: Douglas P. Kingston III ! 6: .AI ! 7: Ballistic Research Laboratory ! 8: Aberdeen Proving Grounds, Maryland 21005 ! 9: <dpk@brl> ! 10: .AB ! 11: .PP ! 12: The Multi-channel Memo Distribution Facility (MMDF) is one of ! 13: the most sophisticated mail systems available for the UNIX\(dg ! 14: .FS \(dg ! 15: Unix is a trademark of Bell Laboratories. ! 16: .FE ! 17: operating ! 18: system. ! 19: MMDF is a mail transport system that supports a variety of ! 20: user interfaces and delivery mechanisms. The design was not encumbered ! 21: with the need to be compatible with existing mail systems, and as a ! 22: result MMDF has a unified family of mail handling programs. This review ! 23: will discuss MMDF's design and operation, concentrating on those features ! 24: that are unique to MMDFII, the latest release of MMDF. ! 25: .PP ! 26: MMDF's design allows it to grow from a ! 27: single-host system to a large mail relay without degradation of mail ! 28: system performance, and to degrade gracefully as the load becomes huge. ! 29: The demands of a high volume mail relay have led to many of MMDF's ! 30: innovative design choices. ! 31: .PP ! 32: Unlike some other systems, MMDF has separate processes for ! 33: mail submission and delivery. ! 34: Recent changes to the delivery software to permit intelligent ! 35: retry strategies based on the retry history for each dead host will ! 36: be explained. ! 37: The effect of the new domain server ! 38: mechanism on address validation will be discussed. ! 39: .PP ! 40: The separation of mail into channels is key to MMDF's ability to ! 41: handle large amounts of mail. Each channel represents a different class ! 42: of delivery and each channel has its own queue. This isolates ! 43: problems and allows one to ! 44: provide different ``levels of service'' to different channels. ! 45: .PP ! 46: Other topics to be discussed will include available user ! 47: interfaces, the mailing list processor, aliasing, runtime ! 48: configuration, and domain based naming. ! 49: .PP ! 50: The MMDF system was originally developed at the University of Delaware ! 51: and has since seen significant development work at the Ballistic ! 52: Research Laboratory and University College London. ! 53: .AE
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