I am running a job that uses SMTP and it can run in excess of an hour, emailing the entire time. It's not my code but a workflow based app so I just get a form to configure the mail server, subj, msg, etc and can't see it's implementation. I know it is .NET and SmtpClient. I have been seeing 4.4.1 timeouts every 10 minutes being reported by the application as the response from the server. The # of emails in those 10 minute sessions are variable, between 100 and below 150 which leads me to ask about the 10 minute timeout time specifically.

I have found there are several exchange properties (though I don't know what version they are running) that set timeout limits. (http://technet.microsoft.com/en-us/library/bb232205%28v=exchg.150%29.aspx)

Would those values for ConnectionInactivityTimeOut and ConnectionTimeout be the controlling the timeouts?

and finally

I would like to ask if exchange considers the consistent connection(s) it kept receiving from the same source as one continuous connection and cause the timeout each 10 minutes and cause the timeout?

I am using a static ip of the mail server.

Thanks if anyone can shed any light on my problem.

EDIT - It is my belief that the library is just keeping the connections around and isn't wrapped in any cleanup code or using statement. That said, I still haven't made any progress on this issue in the last year and just requeue the failed ones as I see them.