IMail "nobody" account losing email

Hi all, I set up a Imail server on my network and configured a nobody
account to catch all unspecific email for teh domain.
Sending/receiving, including for the nobody account, works fine. Except
not all email addressed to a non-existing user gets caught. I should
add that I am generating this kind of email at a rate of 8/minute, but
if I direct it to a normal user's mailbox, all of it gets through just
fine. This function is vital for me, what can be wrong? I would also
mention that I experienced the same thing using a catch-all account
(created via scripts documented by microsoft) on a windows 2003 pop
server, in a different location. Can't one trust the catch-all
capability in servers like IMail and Windows' pop3? I haven't tried
Exchange, but will do so shortly.