problems with qmail-pop3d

[Jeffrey Finkelstein]

I've recently installed qmail on our server and have intermittent problems
with qmail-pop3d as follows: When a user connects via POP to retrieve their
mail, qmail-pop3d does not always correctly identify the fact that they have
mail waiting in their Maildir. The user can check mail for hours and 
eventually they can access the waiting mail.

Does anyone have any ideas where I can start looking or how to turn on 
debugging options?

-jeff