[Dovecot] Recover a deleted message in MDBOX format ?

Hello

Every night a backup of all mailboxes is performed to a NFS mounted partition

All our mailboxes are now in MDBOX format.

I wonder how it would be possible to recover one email accidentally deleted by a user ?

It was easy in MBOX format to extract and save it using mutt ( as root ) from the backuped mbox then re-copy it to the user's mbox.

Of course I should access to the backup mailboxes space using thunderbird but doing this I need to know every users's passwords, that is unacceptable. for security and privacy reasons.

Let users access to the backup space is not possible of course.

Is there a tool ?

Thanks