Review for Stop Ignoring Reply:To by Greg E
Rated 5 out of 5 stars
Worked for me.. TB 52 upgrade started replying to individuals instead of the google groups mailing list I was on.
Installed easily by downloading the .xpi file (whatever that is, I guess it' s like a zip or tar), and using thunderbird -> Tools -> Add Ons -> Extensions -> ("gear" pulldown menu) -> Install add on from file, restart, and now "Reply" works.
To create your own collections, you must have a Mozilla Add-ons account.