Typically, a hang can be any sort of deadlock where the process continues to run, but stops performing a service either for every user, or some, or only one user. A hang in Winroute might not be a hang in the process, but blocking of traffic.
First, check the CPU consumed by the mailserver process
Linux: Use the "top" command.
OSX: Use the "Activity Monitor" in the GUI or "top" in the command shell.