Mail not collecting mail

[Gregory Cortelyou]

Starting this morning the Mail app is not collecting my mail at all. There
is no error message, it goes through all the motions and just  behaves like
there is no mail to retrieve. Entourage will bring in the mail when run
right after. Yesterday Mail asked for my password then asked for it again
and turned up with no mail. I have not changed any settings and when I look
at my accounts preferences they look fine. Anybody had any experience with
this? Entourage is great, but I really do love the simple elegance of the
mail app. 
Greg