Postfix is installed as forwarder to a fixed relay in a system with no
IPv6 addresses (disabled system-wide by net.ipv6.conf.*.disable_ipv6
lines in sysctl). Still, for each message it separately requests both A
and AAAA records of the relay from DNS, as I verified by tcpdump. Is it
a bug or feature? (Yes I know I can explicitly disable IPv6 in postfix
configuration too, but that's not the point.)
My investigation actually started with the following lines in mail.log,
which may or may not be related:
May 4 07:52:16 postfix postfix/scache[1518]: statistics: domain
lookup hits=0 miss=3 success=0%
(3 messages were sent in this interval; there are always 0 hits and 0%
success rate.)
I'm using Postfix 3.1.0-3 under Ubuntu 16.04. Relay is secure.emailsrvr.com.
--
With Best Regards,
Marat Khalili
