Ever wanted to edit the subject lines of a certain important email? Fret no more cos Mozilla has got just the answer for your request with their program called

EditEmailSubject version 2.0.2

https://addons.mozilla.org/en-us/thunderbird/addon/edit-email-subject/

Feedback from some of the users:-

#1
Brilliantly simple, and solves one of the most annoying aspects of email correspondence: receiving an email message with a subject that does not match. Nice work!
#2
This is stupendous! I always wanted this! This is for version 14.0. Just FYI for y’all – this only changes the subject of the message in the main message pane. If you look at the subject in the header bar of the message, it is unchanged – which is good, because it reflects to you what the sender named it.