Exchange Servers (varying version) unable to send mail to specific domain while all other linux servers can.... work around - change send connector to use external dns RRS feed

  • Question

  • Hello,


    I operate several postfix based mail servers and filters as well as some exchange servers.  After some issues with my authoritative dns servers one day, I am no longer able to receive mail from most exchange servers.  The dns issues were resolved by restoring dns servers from backup. After restoring from backup,  Mxtoolbox, dnstools, etc all report that my mx, a, spf and ptr records are correct, all dns servers listed have same records etc, everything looks good as far as I can tell except exchange servers can no longer reach me,  linux based servers are not having any trouble reaching me. The issue has been ongoing for two weeks now.  The bounce back errors from exchange on the senders end dont give a lot of information, " #550 4.4.7 QUEUE.Expired; message expired ##"   Another one forwarded to me said the exchange server was unable to resolve the A record for the mx of the domain.


    I was able to find a work around with one of the sending exchange servers, the administrator of that server changed the send connector to use external dns and the issue was resolved for his domain.  Problem with this workaround is, there are thousands of mail domains hosted on exchange and I will not be able to ask them all to change their servers settings, and they shouldn't have to change anything on their end to fix my problem.


    My question,  has anyone come across a similar/same issue and found a fix that can be done from my end?

    Friday, November 22, 2013 3:21 PM


  • It is difficult to help you because you posted so little specific Exchange configuration information and debugging results.  I would have quickly enabled SMTP protocol logging and looked at the logs to see what is really happening.

    If the Exchange servers are configured to use a smart host, which you seem to imply, then the smart host would be the one generating that error, not the Exchange server, since it would just be sending all mail to the smart host.  I suspect that the problem is with the host Exchange is forwarding to.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

    • Proposed as answer by Amy.Wang Monday, November 25, 2013 8:29 AM
    • Marked as answer by cara chen Friday, November 29, 2013 9:23 AM
    Sunday, November 24, 2013 2:04 AM