Comment 141 for bug 52667

Ok, sorry, I just figured out I made a mistake:
Reply-To-List works, but only when you have configured thunderbird to show _all_ headers.
When you select "normal" headers, the button get's greyed out, cause the extension doesn't find the List-Post header anymore.
Apparently Thunderbird makes only the visible headers available to extensions.
I have another extension installed "Display mailinglist headers" which also only works with all headers displayed.

I'm definitely sure, that in Thunderbird 1.5 both extension worked, no matter how the "Show Header"-option is set.