[Dovecot] is there a way to trigger dovecot to update all users quota usage

We are using the quota plugin and storing people's usage in the (mysql) db.

We have some users that have some mail, but are not really receiving new mail, nor are they logging in to check mail, so they don't yet have a row in the quota table.

Is there a way to cause dovecot to just generate that quota usage?

Ben