Even for single-list messages, I can't see whether ``reply to list'' is
doing what I want unless I have extra information from the sender---
information that can't be communicated through List-Post (because it's
envelope information added by list managers) but that is communicated
successfully through Mail-Followup-To.
You can't see whether "followup" is doing what you want either, even
with Mail-Followup-To. You may decide to trust it to do what you want,
but when you do so you're implicit assuming that the sender who set
Mail-Followup-To happens to want followups to go to the same place(s)
that you do. For instance, you can't use Mail-Followup-To to decide
whether someone is a member of a particular list.
Keith