Plesk 12.x / Windows :: Add Existing MailEnable Mailbox To Configuration

Plesk Windows 12, MailEnable mailserver

I added users directly to mailenable (using their migration utility to import from an old mail server which plesk does not support). The domains exist in plesk but not the individual email users/mailboxes.

Now I want to add those email users to plesk but it doesn't let (not surprisingly), when I try to add a user it returns an error: "Unable to update the mail account properties:mailmng failed: MEAOPO.Mailbox.AddMailbox failed"

My question is: How can I add the users that already exist in MailEnable to the plesk configuration? (i.e. ignore the error and add the user to the plesk database, or even better yet if plesk can read the configuration and add all users)

Tthe plesk kb articles suggest running mchk.exe but that is designed to take users from plesk and add them to mailenable, I need the reverse).