6.2.8 Problems

Mailman will send as many MAIL FROM/RCPT TO as it needs. It may result in more than 10 or 100 messages sent in one connection, which will exceed the default value of Exim's smtp_accept_queue_per_connection value. This is bad because it will cause Exim to switch into queue mode and severely delay delivery of your list messages. The way to fix this is to set Mailman's SMTP_MAX_SESSIONS_PER_CONNECTION (in $prefix/Mailman/mm_cfg.py) to a smaller value than Exim's smtp_accept_queue_per_connection.
Mailman should ignore Exim delay warning messages, even though Exim should never send this to list messages. Mailman 2.1's general bounce detection and VERP support should greatly improve the bounce detector's hit rates.
List existence is determined by the existence of a config.pck file for a list. If you delete lists by foul means, be aware of this.
If you are getting Exim or Mailman complaining about user ids when you send mail to a list, check that the MAILMAN_USER and MAILMAN_GROUP match those of Mailman itself (i.e. what were used in the configure script). Also make sure you do not have aliases in the main alias file for the list.