SonOfThunder, MailQ is only for checking the Linux MailQ and doesn't work with exchange.
jakkedup, found the answer on a Cacti forum.
You can sue the COUNTER argument to check the MailQ in the server performance monitor (PerfMon Counters). Off the top of my head the counter is something like \MSExchangeIS\Mail Queue (or similar)
Edited Mon Dec 19 2005, 11:52AM ]