On 3/22/2017 1:08 PM, Marvin Renich wrote: > Thanks, Wietse and Noel. Once the IPv4 delivery fails for some reason, > and Postfix tries IPv6 (which must fail for this relayhost), the message > is deferred. Do subsequent redelivery attempts only try IPv6? This is > what it looked like was happening, even if the failure was caused by > something else.
Each subsequent attempt will try both, but only the last error is reported in the queue listing. > > The message sat in the deferred queue overnight, with more than a dozen > redelivery attempts, all with the same result, even though during that > time I was able to correctly resolve the relayhost's IP. postqueue -f > failed, but changing inet_protocols to ipv4 and restarting Postfix > delivered the message immediately. If DNS lookups were working, the temporary delivery error was probably something other than a DNS lookup failure. You should be able to find these other delivery attempts logged by the smtp delivery process. > > Also, what about my third question: was the serverfault answer only > useful if an smtp-ipv4 service is manually added to master.cf? That answer is useful for a host that delivers some mail via IPv6 but has some destinations that don't work properly on IPv6 -- for example, a destination that 5xx rejects IPv6 mail, but accepts IPv4 mail. Such workarounds are not required for well-behaved destinations. And yes, a master.cf smtp-ipv4 service would be needed, so it was not a complete answer. -- Noel Jones
