Setting Postfix + Courier + Cyrus: cannot find user dir on authentication
I am trying to adapt a tutorial for setting a mail server in Arch Linux  to Debian. I finished the step of PostfixAdmin, and I perfectly can send e-mails from it and add users and domains to the database. Looking at /home/vmail, I also checked that I can receive e-mails. Before setting up Rouncube, I wanted to try accessing with Thunderbird, but I am getting the message of Incorrect username or password.
Looking at the logs, on mail.log I can see:
Jan 3 00:32:52 cub3 imapd: Connection, ip=[::ffff:126.96.36.199]
Jan 3 00:32:53 cub3 imapd: chdir Maildir: No such file or directory
# ls /home/vmail/
cur new tmp
1325457494.Vca00I4f096M587089.cub3 1325457546.Vca00I4f099M501611.cub3 1325471089.Vca00I4f78fM130501.cub3
So the directories exist... I've rechecked the config files several times (even on different days, as resting is always good :P), and googling around, but no luck about what is wrong. Any advice about where to look for it is appreciated.