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Since upgrading to 14.4 I'm seeing issues with two users who are forwarding mail from their corporate email accounts to personal accounts. Both users are forwarding to different domains but the errors in the delivery log are the same:
09:36:57  Exception: An existing connection was forcibly closed by the remote host
at RelayServer.Clients.SMTP.ClientConnectionSync.SendLine(String line)
at RelayServer.Clients.SMTP.SmtpClientSession.SendLine(String #a8)
at RelayServer.Clients.SMTP.SmtpClientSession.SendData(StreamReader #bJ)
When a forwarded message like this fails, SM attempts to resend the message every second. I'm not sure if there's a correlation but after 6+ hours of resend attempts, the mail server slows to a grinding halt even though the CPU and memory utilization appears to be normal.
It was so bad this afternoon that I couldn't log into webmail (constant progress spinner on the SM GUI). I used a remote desktop session to access the server and it was dog slow. Once conneted remotely I was able to get into webmail and I eventually got to the "Waiting to Deliver" spool page. Three messages had been attempting to deliver to these same 2 recipients since approx. 9AM.
Restarting the Application Pool and website had no effect and it literally took minutes for the server to responds to mouse clicks. I eventually rebooted the server afterwhich everything was back to normal.
This is the second time in 5 days that this has occurred--the first time was the day after upgrading. Again, I'm not sure if there's a correlation but it seems pretty coincidental.
Anyone else seeing similar problems?
Thanks -- Steve