I am recently getting a lot of complaints from Thunderbird users on several lists running on our Mailman 2.1.24 system that when they press ctrl+r for reply, the reply goes to the individual sender and not the list. Mailman is set to strip the Reply-To header and set replies to go to the list. I believe that something in newer Thunderbirds are detecting the list headers and giving the user the option of replying to the author (ctrl+r) and the list (ctrl+l). The only issue is sometimes this doesn't seem to be obvious to our blind subscribers which option to use in Thunderbird.
Does anyone know the precise mechanisms that Thunderbird is using, and whether there is any way to overrite it so we can get the old behaviour back by using the reply function to reply to the list?