[Mailman-Users] "disable_dns_lookups = yes" is a very bad idea
jonathan at nerds.net
Sat Feb 18 05:06:43 CET 2006
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 [18.104.22.168] and not
the IN MX address relay.verizon.net [22.214.171.124].
I added a note to the Mailman FAQ on this page:
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