Problems with imap x pop

[fabricio de Oliveira Delocco]

Hello ALL,

I have an IMP installed in a Redhat 6.2 system running very well, but 
some users are having problems with the imap and pop processes.

They watch their emails at home and get them here with pop, The problem 
is that some of these email get stuck in webmail and do not come when 
they pop their account. One of our users has a 0 bytes archive in 
/var/spool/mail/user but the webmail shows some messages.

Is there another place imp or imap puts the archive?

PS: This happens only to a few and specific users, other are running fine.

Fabricio Delocco