I've followed this guide on setting up a mail server on my dedicated server. I've been able to send mails from the php application I'm using and the linux commandline (using telnet, php, etc).

The problem is that I cannot connect to the server via IMAP/POP which I've setup using Courier. I've tried using thunderbird but it complains that the username or password is wrong. I doubt it is the username/password but I don't know how to trouble shoot this.

Edit: Here's the messages in mail.log:

Jan  9 22:43:38 mail authdaemond: received auth request, service=imap, authtype=login
Jan  9 22:43:38 mail authdaemond: authmysql: trying this module
Jan  9 22:43:38 mail authdaemond: SQL query: SELECT id, crypt, "", uid, gid, home, "", "", name, "" FROM users WHERE id = '[email protected]'  AND (enabled=1)
Jan  9 22:43:38 mail authdaemond: password matches successfully
Jan  9 22:43:38 mail authdaemond: authmysql: sysusername=<null>, sysuserid=5000, sysgroupid=5000, homedir=/var/spool/mail/virtual, [email protected], fullname=peter, maildir=<null>, quota=<null>, options=<null>
Jan  9 22:43:38 mail authdaemond: authmysql: clearpasswd=<null>, passwd=password
Jan  9 22:43:38 mail authdaemond: Authenticated: sysusername=<null>, sysuserid=5000, sysgroupid=5000, homedir=/var/spool/mail/virtual, [email protected], fullname=peter, maildir=<null>, quota=<null>, options=<null>
Jan  9 22:43:38 mail authdaemond: Authenticated: clearpasswd=peter, passwd=password
Jan  9 22:43:38 mail imapd: chdir Maildir: No such file or directory