courier-imap and MS Outlook

Hi there.
Ive got courier-imap running as my mailserver on openSuSE 11.0. As long as Im using up-to-date email clients like Thunderbird everything is ok.
If im trying to connect to the imap server using MS Outlook XP it fails saying something like “server is offline”.
Please dont tell me now use Client something instead of Outlook. I promise I would if I could.
I dont want to change to dovecot either if possible.
Any help is welcome.
Thanks in advance.