Rated 3 out of 5 stars

I've installed this but don't see a "Reply++" button anywhere, and there's no button to add in the "customize toolbar" list.

If I right-click on the message row in the list of messages, "New to all (click)..." does appear. But it doesn't appear in any menu or context (right-click) menu in the message pane itself.

Some screenshots on the addon page would be really helpful so I know what I'm supposed to be looking for.

Doesn't seem to play nicely with Identity Chooser as it always inserts my own address into the cc field instead of matching it to the identical sender address. (Admittedly I can't tell if this is an issue with this plugin or Identity Chooser.)

The addon seems confused about its name: Once installed it's listed as "New Thread to All"; its title on the addon page is "New Email to All" and the description refers to it as "Reply++" -- this made it unnecessarily hard to figure out if it was installing correctly, and find its addon page.

Finally, I was also disappointed that the "Support site" link sends me to an empty GitHub repo. Would certainly file the above review as issues if there were any code to comment on.