Personally, I agree with the choice of responding to the message From:
header as opposed to the envelope from. The message From: header is the
author of the content of the message and if that content is "urgent" in
any way, I would want that person to know I am not being timely.
I am of the opposite opinion. Vacation notices should go to the same
place as nondelivery reports and automatically-generated delivery
notifications - which is to say the envelope return address.
If the author of the message wants to get notifications about whether
and when a message will delivered or read, the standard mechanisms
for this all require that the author's address be in the envelope
return address. I see no reason why vacation notices should not follow
this well-established practice.
In any case, I don't think the primary issue is where to respond but
rather when to respond. A response should only be created when the
address of the recipient appears in either the message To: or Cc:
header.
I agree that this is a useful heuristic, though I don't think it's
sufficient by itself.
Of course, either set of rules means that certain mailing list softare
habits are, shall we say, unorthodox. I am often confounded by which
set of rules is really the lesser of two evils, since at this point
neither is a clear winner.
part of the problem is that very little about list behavior is
standardized, so we get a wide variation in behavior from one list
to another. for instance, far too many lists fail to rewrite
return-path and gratuitously rewrite a half-dozen other headers.
in the past efforts to alleviate this problem have been hampered
because each author of list software truly believed that his way
was the One True Way. but who knows, maybe the world is saner now.
Keith