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- .TL
- MMDFII:
- A Technical Review
- .AU
- Douglas P. Kingston III
- .AI
- Ballistic Research Laboratory
- Aberdeen Proving Grounds, Maryland 21005
- <dpk@brl>
- .AB
- .PP
- The Multi-channel Memo Distribution Facility (MMDF) is one of
- the most sophisticated mail systems available for the UNIX\(dg
- .FS \(dg
- Unix is a trademark of Bell Laboratories.
- .FE
- operating
- system.
- MMDF is a mail transport system that supports a variety of
- user interfaces and delivery mechanisms. The design was not encumbered
- with the need to be compatible with existing mail systems, and as a
- result MMDF has a unified family of mail handling programs. This review
- will discuss MMDF's design and operation, concentrating on those features
- that are unique to MMDFII, the latest release of MMDF.
- .PP
- MMDF's design allows it to grow from a
- single-host system to a large mail relay without degradation of mail
- system performance, and to degrade gracefully as the load becomes huge.
- The demands of a high volume mail relay have led to many of MMDF's
- innovative design choices.
- .PP
- Unlike some other systems, MMDF has separate processes for
- mail submission and delivery.
- Recent changes to the delivery software to permit intelligent
- retry strategies based on the retry history for each dead host will
- be explained.
- The effect of the new domain server
- mechanism on address validation will be discussed.
- .PP
- The separation of mail into channels is key to MMDF's ability to
- handle large amounts of mail. Each channel represents a different class
- of delivery and each channel has its own queue. This isolates
- problems and allows one to
- provide different ``levels of service'' to different channels.
- .PP
- Other topics to be discussed will include available user
- interfaces, the mailing list processor, aliasing, runtime
- configuration, and domain based naming.
- .PP
- The MMDF system was originally developed at the University of Delaware
- and has since seen significant development work at the Ballistic
- Research Laboratory and University College London.
- .AE
-