ubuntu 11.10 32bit. Setup a dovecot imap server. Using Thunderbird on a different ubuntu machine (64bit) to access imap server. Everything else is fine, except I can not compact the deleted email in inbox, which is stored at /var/mail/username. Checking mail.log and I see this error message:

Apr  3 00:10:11 autumn dovecot: imap(username): Error: file_dotlock_create(/var/mail/username) failed: Permission denied (euid=1000(username) egid=1000(username) missing +w perm: /var/mail, euid is not dir owner) (set mail_privileged_group=mail)

what is wrong with the permission? Here are the permissions for the relevant files:

$ ls -ld /var/mail

drwxrwsr-x 2 mail mail 4096 2012-04-02 23:36 /var/mail



$ ls -l /var/mail/username

-rw------- 1 username mail 417 2012-04-02 23:36 /var/mail/username

Anyone knows what's going on here?