Look :
authtest user@domaine.com
Authentication succeeded.
Authenticated:user@domaine.com (uid 5000, gid 5000)
Home Directory: /var/spool/vmail/
Maildir: domaine.com/user
Quota: 10250000
Encrypted Password: cxlCuq3RvE/as
Cleartext Password: (none)
Options: (none)
Here the quota is good. But in roundcube there is nothing...