Rated 5 out of 5 stars
With the new era of IMAP focused mail sync it brings both good and also bad.
Bad being if someone hacks you account and deletes your emails chances are your provider won't chime it help you out with a backup.
Batch copy works really easy by right clicking on the IMAP account and choosing Batch Copy, it then works in the background looking for any new emails in your folders and then backing them up to a local folder in thunderbird.
The only issue I had with this addon was when I got rid of one of my emails and wanted to also get rid of the local copy/backup as there was no option to do so, I contacted the developer and he was quick to reply and helpful.