simonjwiles@gmail.com writes:
Grateful for any insight you can offer! Thanks!
Have you asked Postfix channels? I don't think this is a Mailman problem, and they would recognize the issue faster than we do.
The first thing I would do is grep /path/to/mailman/var/data/postfix_lmtp for the looping address. If it's not in there, then Mailman is not involved in the loop.
I'm pretty sure that what's happening is the domain is recognized because it's in relay_domains, the transport maps are consulted, the address lookup fails, the transport defaults to relay_transport, which defaults to relay, which is in fact smptd, which recognizes a loop because the source and next-hop are both self. Voila!
From the ADDRESS_CLASS_README:
Valid recipient addresses for [relay_domains] are listed with the
relay_recipient_maps parameter. The Postfix SMTP server rejects
invalid recipients with "User unknown in relay recipient table".
If this parameter value is empty, the Postfix SMTP server accepts
all recipients for domains listed with the relay_domains
parameter. [Ie, you're an MX for those domains.]I guess
relay_recipient_maps = hash:/path/to/mailman/var/data/postfix_lmtp
will fix this problem assuming the error message above is acceptable. I can't guarantee it won't cause other problems, though, depending on whether your host provides other services to those domains.
Steve