[R_Edward]

So is it a setting that affects only your own replies? Or is it something you set in an original email or reply that you're composing, that compels all recipients who click the reply button to reply to the entire addressee list by default? Because I can't see much use for the former, but the latter could be really useful.

[afterburner]

The former, which is quite useful, when you keep mistakenly only replying to the previous respondent in a group email chain. When this becomes an issue is when you don't realize what you've done; then the person you replied to might not notice it. And then they might only reply to you since it's not longer a group email... and so on.

[anonymouz]

I'm curious, how would you imagine the second one would even work? Add a new header that asks the mail reader to choose "reply to all" by default? It seems like something no reasonable mail reader should or would respect.

[R_Edward]

That's probably it: a simple boolean header. And I agree that changing default behavior is a very dodgy practice.

I used to have an Outlook extension that disabled Reply-All on outgoing mail. I used the heck outta that thing! Nothing bugged me more than someone sending an e-mail broadcast to the division, which would be followed in my inbox by a dozen or more Out-of-office autoresponders.