Rated 4 out of 5 stars
I've been using your tool in IMAP mode with Gmail for quite a long time and had no problems until updating to Thunderbird 78.7.1.
From this version on, when I edit a subject, the message gets appended with current date instead of its header date.
Thunderbird continues showing the correct date (the header one) and behaves accordingly, but Gmail app/webapp show the message as if it arrived at the time of subject editing process.
This discrepancy between TB and Gmail app/webapp makes your tool unusable for my purposes.
I genuinely think I'm not the only one facing this problem.
Also, updating TB to 78.8.1 doesn't solve the issue.