out of mail hosts to try. putting message in retry queue
This article was previously published as ID#29057

Summary:
Messages to one or a few domains are never delivered - they go to Retry, then are eventually returned.

The event log shows a warning "out of mail hosts to try"

Resolution:
"out of mail hosts to try" means MMS attempted to deliver the message but failed and the message will be put into the retry queue.
this could happen for various reasons including:

1. DNS lookup failed - MMS then has no idea where to send the message
2. DNS succeeded, but MMS was unable to connect to any of the MX hosts found in DNS. This can happen if the DNS info is in error, if the remote server(s) is down, or if there is a network connectivity problem with the remote server(s).
3. DNS lookup succeeded but no MX record was returned. This can be because the remote site didn't publish their DNS info correctly or because your local DNS server gave you incomplete or inaccurate data (could be cached data).

To determine if one of the above is the cause, or perhaps something else, set your SMTP Relay logging level to trace and resend one of the problem messages in Retry. This will generate some fresh log data, and you can trace the message in the Event log to see what the last successful activity was before the "out of mail hosts" message.

Remember to reset your logging level back to Normal after your test or your event log will quickly grow unmanageable.

Additional Info:
see also this technote on the Retry queue

Original Author: ACUNY
Original Submitter: ACUNY
Keywords: retry out of mail hosts dns mx routing tab domains tab tech tip MMS ID#29057