CivicSpace has developed an Organic Groups mailing list manager. It accomplishes several tasks.
1) Keeps Groups members synchronized with mailing list membership by using the group as the mailing list membership.
2) Mail Transport Agent independent - works with Exim and Postfix
3) Dynamically creates a mailing list for each group, good if groups are spontaneously created.
4) Mailing list management, and Drupal management via email with mailcommand.
5) Thread management with comment mover.
We would like to deploy OG2List for http://groups.drupal.org but need people to test and set up OG2List on Postfix following these instructions.
Future development includes porting modules to 4.7 and archive management to remove repeated messages in responses in a thread.