Andreas Freyvogel:
> The email address to which we are sending is "u...@mmm.com".
Postfix will send to the A record for mmm.com if MX lookup is
disabled, or if MX lookup results in a "not found" response (either
NXDOMAIN or NODATA).
Postfix does not send to the A record if MX fails due to any other
error such as timeout or server failure.
If your MX lookups "by hand" succeed and Postfix still sends to the
/etc/hosts address, then something is broken at your end.
Perhaps you have an outdated (or missing) etc/resolv.conf file in
the Postfix queue. With a missing etc/resolv.conf file, some resolvers
will contact the DNS server on 127.0.0.1. And with an outdated
etc/resolv.conf, anything could happen.
Wietse
