Speaking ripe from experience, the Mailman FAQ suggests turning on "disable_dns_lookups = yes" to improve the performance of Postfix with Mailman, which kind of makes sense. BUT in Postfix, this disables all MX lookups. So, unless you are going indirectly through a relay that is going to handle MX lookups for you, Postfix will begin trying to deliver e-mail to stupid addresses.
The symptom was that deferred messages were piling up with "Connection refused" errors, at first I thought I was getting blacklisted or something. Finally, I noticed that e-mail to verizon.net for example was trying to go to the IN A address verizon.net [206.46.230.37] and not the IN MX address relay.verizon.net [206.46.232.11]. I added a note to the Mailman FAQ on this page: http://www.python.org/cgi-bin/faqw-mm.py Jonathan ------------------------------------------------------ Mailman-Users mailing list Mailman-Users@python.org http://mail.python.org/mailman/listinfo/mailman-users Mailman FAQ: http://www.python.org/cgi-bin/faqw-mm.py Searchable Archives: http://www.mail-archive.com/mailman-users%40python.org/ Unsubscribe: http://mail.python.org/mailman/options/mailman-users/archive%40jab.org Security Policy: http://www.python.org/cgi-bin/faqw-mm.py?req=show&file=faq01.027.htp
