This module is probably particularly relevant to sites which operate a large number of Groups and/or Mailing Lists. By implication, you would probably have an existing Mailman system and expertise in Mailman. For new projects, consider whether to use Drupal's own mailing facilities, e.g. with the Notifications, Mass Contact, Simple News or other module.
* Users can easily see which mailing lists relate to their joined Groups.
* Lists can be hidden from users who are not a member of a related Group.
* Mailing Lists can be set auto-subscribe - subscription is triggered when a new member joins a related Group.
* Mailing Lists can be linked to any number of Groups.
* Each Group may have multiple Mailing Lists.
* Integrates with both Mailman Manager and User mailman register modules.
Dependencies and integration
Dependencies: Drupal 6.x, Organic Groups, Mailman Manager. A working Mailman implementation is required for any useful application, and that may be on a separate server.
Optional: User mailman register, og_abt_domains.
Drupal 5.x not supported but would be a possibility.
License and Support
Released under GPL. Commercial support and customization is available from the original developer - www.netgenius.co.uk
Development of this module was sponsored by Initiatives of Change - www.iofc.org
I'm not sure if Mailman Groups has a long term future, as new Drupal installations are likely to opt for a different solution, and existing Mailman users implementing Drupal and OG will quite possibly migrate to a Drupal/PHP based solution over time. I'm looking for one or more co-maintainers, ideally people who are involved with managing a live Drupal+Mailman implementation (I am not currently in that situation.)