Ironport C350 slow to relay messages

Unanswered Question


I've got 2 Ironports C350 that are relaying the email from my exchange 2003 server to the internet.  Recently, users have complained that it takes up to 10min for email to reach their destination.  After investigation, emails seems to stay for a long time in the exchange SMTP queue as queued messages.  Enabling the transport log shows the following error occuring once in awhile :

Event Type: Warning
Event Source: MSExchangeTransport
Event Category: Connection Manager
Event ID: 4006
Date:  15/04/2010
Time:  2:27:35 PM
User:  N/A
Computer: ExchangeSvr
Message delivery to the host '' failed while delivering to the remote domain  '[];[]' for the following reason: The connection was dropped by the remote host.  ( being my C350s running 6.5.1-005)

I'm assuming the problem is with the ironports because if I remove the smarthost config in exchange and deliver the email directly from the exchange server using DNS, deliveries are back to near instantaneous.

I've tried to change the Max Messages per Connection from the default 10 to 100 and changed the Max. Concurrent Connections from a Single IP from the default 2 to 5.  I haven't noticed much improvement from those changes.  If I wait long enough all emails eventually gets delivered.

Where would you start to troubleshoot this issue?

I have this problem too.
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pirato1428 Fri, 04/30/2010 - 06:12

I would suggest to check the connectivity (faulty ethernet cable) (routing if not on same network) it has happened to me before, or some local ethernet errors that might exist. I am assuming though that the incoming mails are delivered on time from the Ironport to exchange and that there arent´t any issues there as well. You could try log into the CLI and grep the maillog or use tracking to see instances of the messages that would have timed out from the exchange and see if those particular errors make sense (o can post here an extract of that log).

And I am assuming here again that your eXchange server IP is listed in your relaylist $sendergroup.

Martin Eppler Mon, 07/05/2010 - 13:10


what do the mail_logs for the ICID in question say? I would speculate that either the maximum connection time or the maximum number of recipients per hour has been exceeded, but your mail_logs should indicate this then.

You can also try to set up an injection debug log in your log subscription and see if the SMTP session fails for one or another reason.




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