We have a very strange situation I don't quite understand. Our postfix server mostly delivers email just fine, but for a number of domains, there is an issue. Those domains are peculiar, as they only have an a record and no MX record in DNS.
The error I am getting is:
host or domain name not found. Name service error for name=<DOMAIN> type=MX: Unknown error 0>
Strangely enough, this is true -- because the MX lookup does fail. There's that A record though, that postfix seems to happily ignore.
We're currently running postfix 2.9.6 coming out of pkgsrc.