I have a weird problem relating to Apple Mail and an IMAP mail server I use. If I use a client such as Thunderbird or Entourage my email works absolutely fine, sends, receives etc perfectly. 

When I try and use mail however I set the account up exactly the same and it will not even display messages in the message pane, almost like its connecting but not getting through. This problem only arose when I upgraded to Leopard. I have two friends using Macbook Pro's who use the same server and same mail domain and it works fine for them, with the same settings. 

THe logs for the server show a connection but Mail never requests anything from the server, even if I explicitly send and receive. 

Any ideas?