I recently had an issue with our windows based Plesk installation where a subscription (hosting plan) for internal use was accidentally deleted.
I attempted to use the Plesk backup system to recover just the emails but as usual when it comes to the Plesk Backup Manager it wasn’t worth the effort (I truly don’t understand why Parallels don’t offer a remote backup service for Plesk as an add-on – I’d buy it).
Fortunately I used a remote backup service that backs up my MySQL Databases and all the files and folders I select (which includes the daily backup of SQL Server databases I have configured), effectively giving me full coverage.
Now I had the worry of how to restore emails from these backups to the server without causing serious issues between the database and what is in the file structure for the mailbox.
Fortunately it seems that all of the mailbox information is stored in files within the mailbox folder itself so as long as your restore (and overwrite) the entire mailbox from your backup over the replacement mailbox you have setup (or the corrupt one if you’re having problems), you should be good to go.
As with anything, this is done at your own risk and I recommend taking copies of all relevant files before performing each step of the operation!