When I compose a new email with Thunderbird, I can "Customize From Address". That's fine.
When I compose a reply, it would be appropriate to automatically customize the from address, to the address the mail I am replying to was sent.
Example:
I ordered something at webshop.com and put an email address in my profile there: "webshopper@mydomain.com". That way, when webshop.com (or their associates) send me an email, they send it to "webshopper@mydomain.com" . When I reply to that mail, I am replying as "myrealname@mydomain.com". I now have to manually customize the from address to be "webshopper@mydomain.com". That should be the default behavior. Thanks.