Florin Pasăre writes:
> I would like to ask you where the system
What do you mean by "the system"? Mailman? The mail servers (these
are the programs that exchange mail between hosts on the Internet)?
Your mail client (the program you use to read and send mail)?
"Something" between the author's fingers and your eyes?
> gets the names you see in the "sent by" field,
What "sent by" field? Do you mean something you see in your mail
client? Maybe the From field? (There is no standard "sent by" field
for email,)
> because sometimes the name doesn't make it clear who is sending the
> email and we would like to know if it is something we can control
> or change.
The mail standard RFC 5322 specifies a "From" field which contains the
address of the author and optionally a display name for them. This is
set by the author's mail client, and according to the standard should
not be changed by anyone else. However, (1) mail clients such as
Outlook and Apple Mail frequently change, interpret, or add random
stuff to the From field when they display the author's identity, and
(2) there is an anti-phishing protocol called DMARC according to which
a sending system can request rejection of mail claiming to be from
that system unless a valid digital signature is present. Since some
things that a mailing list does (like adding unsubscription information
as legally required in many places) break the signature, Mailman has
an option to change the From field from "Some User <u...@domain.tld>"
to "Some User via This List <l...@listhost.tld>". This DMARC
mitigation is only used if the list owner explicitly configures it.
> Another question is where the system gets the name of the person who
> appears in the "reply to" field.
According to RFC 5322, that field also should only be set by the
author of the original message. However, nonconforming behavior is
common, and under certain circumstances Mailman will set that field:
1. By default, Mailman will not touch that field, but will pass it
through if it exists.
2. When configured to do so, Mailman will add a fixed address
(usually the list's posting address) that the list owner
specifies to Reply-To.
3. Alternatively, when Mailman is configured to change the From
address to mitigate rejections at subscribers' systems due to the
DMARC protocol, Mailman will add the original From address to
Reply-To.
I think in the case of setting Reply-To to an specific address, the
list owner may specifically ask Mailman to remove other addresses. I
don't think that any mail servers (such as Postfix or Exchange) ever
touch Reply-To.
> I've already seen wrong/different than what was expected names
> twice using Mail on Macbook. The message is sent, for example, by
> Mario Rossi, and the system adds his email address to the cc.
I don't recall for sure if there are circumstances where Mailman
changes Cc, but I'm pretty sure it never does. I don't think that any
mail servers (such as Postfix or Exchange) ever touch Cc, only the
originating mail client does.
> The problem is the reply-to field, because there one sees the name
> of, for example, Claudio Bianchi, which has nothing to do with this
> message and so I don't understand why his name appears above the
> general address of the mailing list.
What do you mean by "above"? Please quote exactly what is on screen.
(Sorry, this list doesn't permit screenshots.)
> With MS Outlook instead what one sees in the sent-by field is the
> following: list name list-boun...@domain.ext on behalf of XXX via list name
> l...@domain.ext.
By "sent-by field" do you mean the "From" field?
That sort of looks like something Mailman might produce, but not
exactly (which means Mailman did *not* produce it). I believe in the
case of DMARC reformatting Mailman produces the "XXX via list name
<l...@domain.ext>" portion, but it will *definitely* not put
"list-bounces" anywhere in From. Check that you are quoting exactly.
If so, I think that is Outlook hallucinating. Outlook definitely
displays garbage under some conditions, and I think I remember this
particular problem being an Outlook misfeature. Specifically, it
grabs the content of the "Sender" field and puts it before "on behalf
of".
> Is it possible to have l...@domain.ext instead of
> list-boun...@domain.ext?
The <list-boun...@domain.ext> is the address Mailman puts in the
"Sender" field (normally not displayed by mail clients). If Sender is
present in the mail header, mail servers send various administrative
messages to Sender rather than From or Reply-To, including
non-delivery messages. You do not want to change the "Sender" field
to the list-post address, because all those administrative messages
would then go to the list, and many would likely be distributed to the
subscribers. You do not want to remove the "Sender" field, because
without it such messages would go to post authors but they probably
cannot do anything useful with them (and sometimes there are many for
just one post).
> If you have any hints for where to look or any ideas, it would be
> great.
My suspicion is that you are stuck: the problem is that the mail
clients you are using do a very bad job of presenting header
information. I'm not going to tell you to change clients, but I can't
think of anything you can change in Mailman that would make it work
better with Outlook or Apple Mail.
If you want to see if there is *anything* we can do:
Start by quoting exactly what you see on the screen, and continue to
specify the mail client used as you did in this message. The problem
is that the mail standard provides a minimum of 6 different ways to
specify who sent a message, each with well-defined, unique meaning to
mail programs. None of them are called "sent-by", and "good" mail
clients report the header fields using the technical names precisely
to make conversations like this one go more smoothly. An exact quote
of the full header information as presented by the mail client will
help us guess more accurately what is going on.
Do not say "the system does X" unless you (1) identify which program
is doing X and (2) you are quite sure that that program is the one
that is doing X. If X is what you see on screen, say that, and what
program you are using to view that content.
If possible, use an open-source mail client such as ThunderBird to
view the message and report what you see there. Outlook and Apple Mail
both present the message in ways that make it difficult to understand
what the message header actually contains.
Regards,
Steve
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