POP3 Timeout issues on 10.8.2 e-mail server

Anyone else seeing this in their mail server logs on 10.8.2 server:

log[3153]: pop3-login: Error: Timeout waiting for handshake from auth server. my pid=3308, input bytes=0

I have about 40 users on the server. Some connect with IMAP, but about 2/3 are still connecting to the server from Outlook 2007 using POP3. The errors are most prevelant when mail.app is open on my computer (which is opening every account on the server w/ IMAP). I thought it was due to a limitation on connections, but unless I haven't found the setting/file yet, that doesn't appear to be the case. The e-mail accounts are setup on active directory user accounts on our domain. I have modified the following files:

20-pop3.conf

mail_max_userip_connections = 1000 (Note: original value was 6)

20-imap.conf

mail_max_userip_connections = 1000 (Note: original value was 20)

Another clue appears to be that occasionally some users accessing the mail server from Outlook using POP3 get authenticated against OD (which fails) instead of AD. I'm not sure what's triggering that. Restarting the mail service does not solve the issue, though restarting the server does.

Eventually, I would like everyone to access their mail via IMAP, but in the interim, I need to run mixed-mode.

Thanks in advance for your thoughts!

BK