dovecot-sql.conf
...
user_query = SELECT CONCAT(home, maildir) as maildir, uid, gid FROM mailbox WHERE username = '%u'


dovecot: Aug 26 20:04:08 Info: auth(default): master out: USER  3       lix@nezz.be     maildir=/usr/local/virtual/nezz.be/lix@nezz.be/ uid=125 gid=65534
dovecot: Aug 26 20:04:08 Info: imap-login: Login: user=<lix@nezz.be>, method=PLAIN, rip=127.1.0.1, lip=127.1.0.2
dovecot: Aug 26 20:04:08 Info: IMAP(lix@nezz.be): Effective uid=125, gid=65534, home=
dovecot: Aug 26 20:04:08 Info: IMAP(lix@nezz.be): maildir: data=/HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB/Maildir
dovecot: Aug 26 20:04:08 Info: IMAP(lix@nezz.be): maildir: root=/HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB/Maildir, index=/HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB/Maildir, control=, inbox=
dovecot: Aug 26 20:04:08 Error: IMAP(lix@nezz.be): mkdir(/HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB/Maildir/cur) failed: Permission denied
dovecot: Aug 26 20:04:08 Error: IMAP(lix@nezz.be): mkdir(/HOME_DIRECTORY_USED_BUT_NOT_GIVEN_BY_USERDB/Maildir/cur) failed: Permission denied