[Dovecot] Default mbox file ownership and permissions with static userdb

Hi there!

I'm using Dovecot 1.1.7 in a simple setup with a static userdb:

userdb: driver: static args: uid=50018 gid=50019 home=/home/dovemail

When my users create folders via IMAP, the ownership of the mbox file is user dovemail, group dovemail, and permissions are 600. I'd like this to change to user dovemail, group doveusers, permissions 660, but I can't figure out a way to do it. Can anyone help? Thanks in advance.

-- Cheers, Christian