Review for Reply In Group by John Corliss
Rated 5 out of 5 stars
I wish this extension would be updated. To get around current version compatibility, I've modified my copy of this extension's .xpi so that it works with the current version of Thunderbird, and it does so without any bugs, as far as I can see.
Using the additional button that this extension makes available is a very convenient way to create a reply message that you KNOW isn't going to be cross-posted to several newsgroups.
To create your own collections, you must have a Mozilla Add-ons account.