[Dovecot] batch convert mbox to maildir

Hello, I have used mb2md for an individual user like this:

su ~username cd ~ ./mb2md -m

This converted /var/spool/mail/username mbox to /home/users/username/Maildir just as I expected.

To convert 100s of users the same way would be a chore (su as each user for permissions, etc.).

Is there a way to batch process all /var/spool/mail/$USER to /home/users/$USER/Maildir with the correct permissions/file owners for each user?