"I tried switching to high-performance mode yesterday.. It seemed to end up with sort of the same results, though harder to diagnose. Each process I guess ended up hitting the login_process_size = 64 max and then stopped responding."
We had this same problem, and switching to high-performance mode helps. However, finding out which user or application is logging in, and controlling the end-user is the only way to fix it. In our case it was a multi-threaded application that used IMAP (excessively). Monitoring the maillog should help point you in the right direction. Dozens of these per minute should throw up a red-flag: May 16 17:36:16 <hostname> imap-login: Login: <user> [::ffff:<IP_Address>] Joe
