Editing IMAP header creates new copy Rated 4 out of 5 stars

In common with some other reviewers I need to edit the header of the IMAP email so that the change to the subject appears to other users and/or mail clients. I can do this by turning off the "Local Only" option, however it then creates a copy of the email with the new subject ... and doesn't delete the original.

This review is for a previous version of the add-on (2.0.3).