This documentation is for Dovecot v1.x, see wiki2 for v2.x documentation.

Missing mailboxes

Dovecot by default doesn't use any "personal IMAP namespace prefix", which clients often call either "IMAP namespace" or "IMAP prefix". With Courier you probably had this set to "INBOX.", with UW-IMAP you might have set it to "mail/". So, the solution is simply to set this field empty and restart your IMAP client.