What are you running the max threads value (g_thread_max) on the server?  I currently am getting steady reports like this:

Thread limit issue, examine status.threads to find cause of issue links=870 max=1000

The majority of the connections are from IMAP clients, then warnings get hit when we have pop bursts from customers who run servers that check 50 or so accounts at once.

I have read through the FAQ at http://www.netwinsite.com/surgemail/help/faq.htm#timeout, but there is still no indicator of a rule of thumb calculation that can be used? eg: 500 threads per cpu, X GB ram per threads, combination of both?  

Thanks