I have the opposite question to that in Thunderbird: How to reply with same E-Mail (when multiple identities)? ! I have lots of different email addresses -- work ones from several previous employers, contact addresses for projects that I support, etc., and a GMail one to which everything gets forwarded.
Apart from a few special cases, I pretty much always want my emails to be sent out from the same address -- a long-term work-related one that should remain unchanged when I change employer. (If this sounds weird, I'm employed by universities to work on projects at a big collaborative lab: my lab address is the one that won't change and which I want to use almost all the time.) But I also want Thunderbird to know that those other email addresses refer to me, so don't include them in the CC field when I reply-all.
As it says at https://support.mozillamessaging.com/en-US/kb/configuring-email-aliases (and quoted on the other SU question mentioned above):
When you reply to a message, Thunderbird uses the identity that matches the address the message was originally sent to, if it can find a match in the account you are working in.
Is there a way that I can make it not do this? I think this just applies to the default identity, so for those few special cases I can manually override. At the moment I have a bunch of identities set up, but as quite a few are now just "backward compatibility" forwarding addresses and I can't send from them, they should definitely not be used as send addresses. Maybe Thunderbird's identities mechanism isn't the right way to declare this sort of "don't put in th CC" address.
Thanks in advance. I didn't find anyone else reporting a need to do this -- is it an unusual situation? Doesn't feel weird to me ;-)