Noel Jones put forth on 8/27/2010 8:58 AM: > Yes, this was rejected by reject_unknown_client_hostname. > > Yes, it appears the client's DNS is working correctly /now/. > > The mail was deferred with a 450 code. This implies that there was a > temporary DNS error of some type. Just because dig works now doesn't > guarantee that it worked when postfix asked earlier.
If the OP isn't currently running a caching DNS resolver on his MX, I'd suggest he do so. It helps curb many of these transient DNS lookup failures. I installed pdns_recursor on my MX a while back and it has helped quite a bit with issues similar to this one. Doing so also decreases lookup latency which can increase performance a bit. -- Stan
