Rated 1 out of 5 stars

This is the extension i was looking for. Unfortunately I cannot use it because:
It does not work between IMAP and LOCAL folders. All emails are marked as new!
When an email message is stored in a local folder Thunderbird adds some extra control records. (x-mozilla....). Copy Folders should ignore these records when comparing IMAP and LOCAL folders.

This review is for a previous version of the add-on (1.61).