The management software running this list is performing reply-to
munging, and probably should not be doing so.
I noticed because a few minutes ago, I tried to send a friendly,
off-list, notice to someone that he had seemingly sent a message
intended only for colleagues at this place of business to the whole
list. My message bounced back from Sympa because 1) I forgot to address
it from my mailing-list-specific address and my regular address is not a
subscriber to this list, and 2) Sympa is setting the reply-to header to
the list (known as “reply-to munging”), so whether I instruct my MUA to
reply to the list or to reply to the sender of a message, it’s going to
go to the list.
“Reply-To” Munging Considered Harmful
“Reply-To” Munging Still Considered Harmful. Really.