Author Topic: Exchange Queue/Transport Errors with Mail Plugins  (Read 4939 times)

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Exchange Queue/Transport Errors with Mail Plugins
« on: March 21, 2006, 07:41:02 PM »
A client of mine uses Avast Enterprise and about a week ago their outgoing mail started hanging up in the Exchange SMTP Virtual Server queues.  Email to some domains would be delivered fine, email to others would never be delivered and would sit in the queue forever.  Incoming mail is apparently always delivered.  Nothing changed on the server that we know of except parhaps automatic updates from Avast and Microsoft/Windows Update.

More testing revealed two separate symptoms.

1.  For the problem domains, we would see in the Application Event log
Source MSExchange Transport
Category SMTP Protocol
Event ID 7010

This is an SMTP protocol log for virtual server ID 1, connection #41. The client at "xx.xx.xx.xx" sent a "xexch50" command, and the SMTP server responded with "504 Need to authenticate first  ". The full command sent was "xexch50 1012 2".  This will probably cause the connection to fail.

And the message would never be delivered.  I found some info on from Microsoft that this is a normal and the servers should fall back to not using the xexch50 command.  Apparently the use the DATA smtp verb of something like that.  In our case there was no fall back and the mail stayed in the queue.  Some users on the internet said they were getting this error with Symantec AV, so I thought it may be the same with Avast.  Disabling the Avast providers did not fix the problem, but uninstalling Avast did fix it.

2.  Mail was delivered fine for a day, then it stopped going out, again only to certain domains, and these domains were different from before!  Domains that were problems before are working properly.  New ones are not working, particularly anything sent to any address hangs in the queue.

This time, there is no SMTP transport error.  And I can see the xexch50 entry in the logs, but it is falling back correctly and so this error is no longer a problem.  There seems to be no error reported for the problem domains, the mail just does not go.

If I disable both Avast exchange providers (Exchange and SMTP) AND I restart the SMTP Virtual Server, then this stuck mail goes out fine.  If I renable either provider, the mail gets stuck again. 

At present, we have Avast disabled, but installed, to allow the mail to work.

Any insight on what is causing this or why it would just mysteriously start doing this?

The server is 2003 w SP1, and Exchange was 2003 SP1, but was updated to SP2 as part of the effort to fix this.