Wikipedia
Ezmlm
ezmlm is mailing list management software (MLM) by Daniel J. Bernstein. It is similar to GNU Mailman and Majordomo but only works with the qmail mail transfer agent. It is released into the public domain. The latest version, 0.53, came out in 1997.
The related program ezmlm-idx originated as an add-on to ezmlm. It now exists as a complete package on its own, but can still be considered essentially as an extension to ezmlm. It adds multi-message threaded message retrieval from the archive, digests, message and subscription moderation, and a number of remote administration functions. The latest version, 7.2.2, was released May 15, 2014.