I have been having issues sporadically with our email queue. I am running Exchange 2000 (sp3) on a Windows 2000 Sever machine. I have all the latest security/critical patches and the hardware should be more than enough to satisfy our demand/load.
We do several mass emails a month on behalf of our clients to the tune of 400-4000 recipients with sizes of up to 2MB. We use an application developed in-house to create these mass messages and then relay them through the exchange machine. Every 7th or 8th time we do one of these mass emails, our outgoing Exchange SMTP queue will stall and Outgoing mail will either go really slowly or not at all. I have used exchange system manager to locate the oldest message(s) and purge them and have also used restarting the MTA Stacks service as a troubleshooting measure. It usually is the case though that I wind up rebooting the Exchange server and 9 times out of 10 this is fixed. I have tried to make sure that these email "blasts" go out late in the day in case we have problems, and also religiously reboot all of my servers on a 2 week schedule. Unfortunately for us, sometimes our clients demand that information get out to their audience on their schedule, not mine.
I have done a good bit of research on Google Groups and the Knowledge Base, only to find that no proposed solutions really work for my situation.
I will say that I don't think the problem lies with our in-house application but with Exchange. I have read that this is a known problem but don't have the known answer.
Any help is appreciated, and I will be happy to provide additional information as necessary.