[Mailman-Users] Problems using Postfix with Mailman

[Stephen J. Turnbull]

Christopher Adams writes:

 > Yes, you are so right. I did have an entry for 127.0.0.1  localhost in
 > /etc/hosts, but also the entry for IPV6, which I didn't need and it
 > apparently took preference.

This is a general property of IPv6: where available it takes
precedence.  Unfortunately, the definition of "available" used by the
low-level stack where this preference operates (ie, I can connect to
the port and get a TCP/IP-level response, including rejection) often
fails to conform to the human idea of "available" (ie, the resource
content is delivered).

That's way over-simplified, of course, but it's worth being aware that
enabling IPv6 may require configuration changes throughout your
application stack.  (And the way things are these days, with IPv6
being more and more important, you may get IPv6 without asking for it
in an OS upgrade or something.)