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I swapped over from SonicWall to a Cisco ASA. Everything seemed to work except now some of my Exchange email gets stuck in the external queues. I get errors 421 4.4.2 Connection Dropped and 451 4.4.2 Timeout errors.

But it is not all email. I can send a message to gmail and it works like lightening. Someone else sends to gmail and it sits. Then any message I send to gmail after that sits in behind for 30 to 180 minutes. But I can send to other domains no problem. It is not limited to gmail, this happens to several domains but there is no pattern.

There is one user who this happens to routinely but it is not restricted to him.

I have rebooted exchange, cleared the queues, changed my transport settings from straight out and through a smarthost, run exchange analyzer and done my updates. Same thing.

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up vote 3 down vote accepted

Seeing your firewall's config would help, but, try turning off inspection for the protocol - look for an active policy-map with inspect esmtp, and remove that protocol from inspection.

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Removing esmtp from inspection did the trick. Thanks! I wonder why? I'll go look at the doc and see if I need to tweek something on my mail server. Thanks for your help! – Peter S. Sep 15 '11 at 13:30

I would recommend running a packet capture on the Exchange server and keying on DNS lookups and SMTP communications. This should give you some clues as to where the problem lies.

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