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 Perhaps you have an outdated (or missing) etc/resolv.conf file in the Postfix queue.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 And with an outdated etc/resolv.conf, anything could happen.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