Exchange 2007/10 - “ 451 4.7.0 Timeout Queues Timeout”

During last years we faced to a very strange problem along Exchange queues that got stacked with a rarely and particular error:

“ 451 4.7.0 Timeout”

To better undestand where it was problem we enabled verbose logging on each Exchange server Hub Transport that faced problems to send intrasite and externally emails:

There was “ 451 4.7.0 Timeout” as you can see.

Then we executed ping command with a particular parameter to understand if there was some packed dropped during connection:

And ping computer_name or IP_address -f -l 1472 was unsuccessfully. ( )

So, following this article, we understood that it was a networking problem and we opened a major case to MPLS provider and we solved after their intervention.

[update 2016.06.07]

Here they are articles about MTU and ping parameter and how to enable verbose logging on exchange server about send/receive connectors

How to Troubleshoot Black Hole Router Issues

SMTP Routing in Exchange 2010 (Part 4)