Can’t get IMAP mail from server

Hi, We are using imap to pick our mail up from our server. We are using Apples Mail program. We can all mail out with no problems but non of us can get our mail from the server? I can see it in each persons mail directory /var/spool/imap/users/username the mail is coming in. I can look at it and see that it is new mail I've sent from another server. So does any one have an idea why we can't get it? This server was move when this started and IP was changed. Evrything else on the systems is working since the move. Thanks. Pat.