Quoting Antony Stone (Antony.Stone@???):

> PS: Please do not set "Reply-to" on list emails.

Actually, _that_ use of the header was harmless (albeit, um, pointless).
Josef had:

To: Josef Grosch <jgrosch@???>
Subject: Devuan AMI
Reply-To: Josef Grosch <jgrosch@???>

...where you'll note that the bottom header repeats his posting address.
The proper use of Reply-To as per RFCs 2822 and 2369 is, quoting
verbatim, to indicate the mailbox(es) to which the author of the message
suggests that replies be sent. Which is to say, direct (in the case of
mailing list traffic) offlist replies.

Josef was implicitly saying, 'Instead of sending me direct mail at my
jgrosch@??? posting address, kindly instead use my alternate
mailbox, jgrosch@???.' Those being the same address renders the
header more than a bit pointless and basically a NO-OP -- but it isn't
_harmful_.

You are perhaps confusing this matter with the Flamewar That Shall Not
Be Named, the _other_ use of the header that was finally ruled
illegitimate in 2001 (although technopeasants keep demanding its
forced application, in less-clued places than Dng).
http://linuxmafia.com/~rick/faq/netiquette.html#replyto

To illustrate the legitmate use-case, consider my recent situation when
I knew I would be about a small ship for a while, hence having irregular
if any Internet access. In that case, I might wish to signal in
outgoing mail an alternate direct-reply address where I might use
webmail. (My linuxmafia.com server doesn't have webmail.) My wife
Deirdre's deirdre.net server does have webmail, so I might do:

From: Rick Moen <rick@???>
To: dng@???
Subject: On the ocean, next week
Reply-To: Rick Moen <rick@???>

This says 'If you happen to send a direct reply to this message, I'd
prefer that it go to my alternate rick@??? mailbox, rather than
to the one I'm sending this from. Thanks.'