> On Jul 12, 2017, at 10:08 AM, Tom Hudson <tom.hud...@giacom.com> wrote: > > Firstly, apologies if I haven't included all of the relevant information in > this initial post. Please let me know if I have missed anything. > > I am currently running Postfix 3.2.0 and have a problem relating to MX > records and defered messages. What I have identified is, if a domain our > server is trying to send to has an MX record which returns no response, the > message is defered. Every time postfix attempts to redeliver this message, > it uses the same lowest priority MX record.
That is not how Postfix generally works. No further information is possible without the relevant logs, and any relevant transport table and master.cf settings. > I have found examples in our mail queue which are deferred with the reason > "unknown mail transport error". When I attempt to telnet to the MX records > for their domain, their lowest value MX is not contactable but the others > are. "unknown mail transport error" is a serious problem, which indicates a delivery agent crash or similar failure to report delivery status to the queue manager. You will find the cause in your logs: http://www.postfix.org/DEBUG_README.html#logging -- Viktor.
