I'm not sure if this is the correct place to post so please point me in the right direction if not.
I'm running IIS7 on Server 2008 R2 x64. I'm running Parallels Plesk 9.5 and smartermail 7.5, smartertrack, and smarterstats. I have about 20 domains and nearly 250 email accounts. All on a server with plenty of resources.
We ran for nearly a year without a single hiccup. We perform updates on all products routinely so everything is up to date. About a month ago we started experiencing a very peculiar problem. All of the sudden the smartermail app pool will stop processing external connections. Meaning I can login to the server remotely and connect to smartermail via localhost but any connection originating from outside the server just keep processing like it's trying to load the login page but never does. It never actually errors out on the client it just keeps processing until they stop their browser or I recycle the smartermail app pool. Now keep in mind that during this issue absolutely every website, plesk, smartertrack, smarterstats, etc is working perfectly fine and the smartermail app pool appears to be running perfectly fine as long as you're connecting from within the server to localhost. This is a managed dedicated server and the hosts entire support team can not figure out what is going on here and they have numerous servers with the exact same setup. We have adjusted the timeout settings, the ping settings, switched it from x64 to x32 and back again. Which by the way the x64 offers superior performance and memory management over the x32 setup. And probably a few other things but we are now at a loss. This problem is intermittent and has happened numerous times a day or only once in a weeks period. During peak traffic times and at 2a.m. when no one is on.
Technically nothing that should affect our system changed. About 2 weeks before the problem began I signed up a new client that added about 40 email accounts. This shouldn't be a problem because I have read about people that have 1000's of smartermail email accounts and 100's of domains. From a hardware/software resource stand point I should be able to quadruple the current load before straining the server so I really don't believe this is the problem.