Reply-To header

Mike Meyer mwm at
Tue Oct 4 18:59:52 CEST 2005

Steven D'Aprano <steve at> writes:
> Mike Meyer wrote:
>> When I notice that a list is broken (RFC 2822 says that
>> reply-to is for the *author* of the message; anyone else setting it is
>> doing so in violation of the RFC, and hence broken, no matter how
>> useful it may be),
> Since when did obeying the RFC become important in and of itself?

Since we started worrying about software being interoperable. If you
only use software from one monopolistic vendor, then that won't matter
to you, and you'll create pain and suffering for everyone who doesn't
drink the same koolaide. But such attitudes seem endemic on the
internet these days.

> That's what reply to means, surely? What is the point of a reply-to
> header that must be the sender, since you already have a header that
> gives you the sender.

You misunderstood. By "for the *author*", I meant that it's for the
*author* to set, not for someone else to set. I did not mean that it
had to be set to a specific value. Saying that anyone else setting it
is broken should have made that clear.

> I have been known to change the reply-to address from the address I am
> sending from (me at work for example) to the address I want the reply to
> go to (me at home). There are many times I'm emailing people I know can't
> cope with the complicated task of changing the To address of their
> reply, so I change the reply-to header so that their reply goes where
> I want it to go to (which might be another email address of mine, or a
> different person, or a mailing list).

And these are perfectly valid uses of reply-to. You're the author,
you're the one that reply-to is there for.

> If the RFC says that the reply-to header doesn't actually mean the
> address the reply should go to, but only the sender, then the RFC is
> broken. "Where the reply goes to" is a *human* decision, not a
> technical one. If I send you an email saying "Please reply to
> president at" then your mailer should honour that
> (although, since we are all adults, you should have the freedom to
> ignore my request and make a nuisance of yourself by emailing your
> reply to a different address).

That isn't what the RFC says, as you could have easily checked. It's
also not what I said.

> Likewise, if I set the reply address to the list, then your mailer
> should reply to the list. Perhaps you can argue that *my decision* to
> have replies go to the list is a bad one, but that's a social issue,
> not a technical one.

You're the author of the message. If you set the reply-to, that's
fine. If anyone other than you sets the reply-to, that's broken.

>> I tell my mailer to ignore reply-to on mail from
>> that list. Similarly, I no longer try and explain to people how long
>> lines violate RFCs and are a pain to read in well-behave mail readers,
> By "well-behaved", do you mean "can't cope with long lines"? How
> curious -- that's precisely the opposite definition of well-behaved I
> use.
>> or why mail readers that wrap text/plain content are broken.
> Curiouser and curiouser. Again that's the exact opposite of my
> definition of broken.

Like I said, I gave up on this fight. Ignorant people are going to
continue generating ugly, hard-to-read messages and complaining when
they get a message that demonstrates why their software is
broken. That's life on the internet these days. The internet used to
be a nice neighborhood. Now it's full of selfish jerks, and there are
to many of them to fight.

Mike Meyer <mwm at>
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

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