Server receives email but user not?

Hi, I have a really weird problem with OS X Server 10.2.8. It host NetInfo network domain, nat, dns, web and I would like to get email working. I set all fields in the server settings panes and the results are: a] I'm able to send email without problems b] server is receiving emails c] user, who sent email, never receives a reply I checked logs and the reply really comes back, but it's stored in /Library/AppleMailServer/AppleMail/MailStore/_current date_/_serial number_ pop3 log says, that the user successfully logged in/out but no email appears in the mailbox. Any ideas? THX. Robert