We're running a single Exchange 2003 server on a Server 2003/XP network. Mail flows from the Exchange SMTP Virtual server through an Exchange connector to an SMTP server and out through a NAT server to the internet. Recently, I noticed that some SMTP sessions in the SMTP virtual server don't time out. Even though I set the connection timeout to 10 minutes, I would often find sessions that had been around for several hours or more. If I let this go and don't terminate the old sessions, after a while we are unable to receive mail and sometimes unable to send. At this point I usually can'trestart the SMTP server or do an iisreset. Often, even if I am able to restart or reset, this doesn't cure the problem. At this point, a reboot is necessary.
After some research, I removed NAV Corporate from the Exchange Server (we have it on the SMTP server and all desktops) and lowered the number of connections to 20 and the connection time out to 2 minutes. It worked fine for a short time, but then it wouldn't let go of SMTP sessions. At this point, I am checking the server a couple of times a day and terminating the older SMTP sessions to prevent a hang. Any suggestions would be greatly appreciated.