SYMPA -- Systeme de Multi-Postage Automatique 

SYMPA is an electronic mailing list manager. It is used to automate list
management functions such as subscription, moderation and management of 
archives. SYMPA also manages sending of messages to the lists, and 
makes it possible to reduce the load on the system. Provided that you 
have enough memory on your system, Sympa is especially well adapted for big 
lists. For a list with 20 000 subscribers, it takes 5 minutes to send a
message to 90% of subscribers, of course considering that the network is 
available.

Developed by elixus.org and supported by OurInternet, Inc, sympa-elixus is
a beefed-up branch based on the latest release of SYMPA.  It features a
Template Toolkit based UI framework, PO-file based localization, and is
generally much more internationalized.

WWW:    http://www.sympa.org/