[Dovecot] Migrating mail from mbox to maildir using dovecot

Hello,

 Currently our mail server is setup to use postfix and dovecot, which is fine except it is setup to use mbox format mail. That and procmail as we need to move to sieve but that is a different issue. I have searched until blue in the face and cannot find a 100% working solution that doesn't require alot of manual interaction to move the mail boxes from mbox to maildir. 

I have tried the mb2md.pl stuff but with over 150+ users that can get tedious having to log in as each one of them to migrate them. I also tried the convert plugin located here: http://wiki.dovecot.org/Plugins/Convert but it kept erroring about not able to convert the box and exiting. We have approx 200GB of mail total that needs to be migrated. Maybe I am just simply missing something but is there a way that we can migrate all the users with minimal end user interaction and minimal administration time? We need this done asap as our backups are killing us with the large mbox style files.

Thanks in advance for any and all input to this.

Donny B.