restoring lost email with Horde and maildir

I have a user that says that a bunch of their emails were deleted when they attempted to login to Horde to read them. I don't know the circumstances, but I do have a backup of the emails. I want to combine the backup copy and the current copy of the emails for their account so they can read them in their Horde inbox.

I thought it would be as simple as copying the email files from my backup to the appropriate /cur directory and making sure the ownership and permissions were correct. But Horde must be tracking messages somewhere, because it doesn't recognize the ones I copied from the backup.

Upon closer inspection I found that a file called courierimapuiddb lists all of the message numbers and file names. So I edited that to include the emails from the backup. That prevented Horde from seeing any emails - old or new.

Does anyone know how I can do this?

Thank you.

Scott