Hi Steve,

Somebody (maybe me) forgot to send this to the list.  Since you
mention Mark, I'm sure "to list" was your intention, and I'm going to
quote in full as well.

Steve Brown writes:

 > Thanks, other Steve. I know so little about Alter Messages and
 > DMARC mitigations that I basically left all those settings at their
 > defaults unless I was advised otherwise by the MM3 hosting service
 > (Mailmanlists.net out of Australia).

Internet mail is very complicated.  I am somewhat familiar with at
least 50 documents describing how it's supposed to work (sometimes
multiple editions of the same one!), and I discover new ones that I
really ought to learn about several times a year.

 > First strip Reply-To:  nothing; neither Yes nor No is checked

Pretty sure this defaults to "No".  To my mind, this should never be
done (it means that there may be no way for an MUA to automatically
identify and reply to author, and our "anonymous list" style does this
anyway so it's not necessary for that purpose), but it is often done
by discussion lists that want to keep traffic on-list.  I recommend
you set it to "No" so you don't have to remember the default.

 > Reply goes to list: No munging

This is preferred by people who discuss sensitive matters (it reduces
accidental distribution of mail intended for specific recipients).
Strictly speaking, the Internet standard for the corresponding
header's use says that it is to be *set* by the author *only*, but
many mailing lists set it to the list to "encourage discussion".

 > Explicit reply-to address: nothing; box is empty

This only affects anything if "Reply goes to list" is set to explicit.

 > DMARC mitigation action:  Replace From: with list address

This is the recommended setting.  "None" is impractical because many
recipients will reject a lot of mail, which will be recorded as
bounces for those recipients (who are doing nothing wrong).  "Wrap" is
impractical because there are a number of popular mail clients (Apple
Mail, for one) which make it almost impossible to read the mail.  And
reject and discard mean that those authors can't post to your list at
all, but they usually can't affect their email providers' DMARC
policies.

 > DMARC Mitigate unconditionally: Yes

This one you should talk to your subscribers and maybe your provider.
"Yes" means that *all* posts will have From changed to the "Steve
Brown via a-l...@example.net" form.  An alternative is to set it to
"No", which means that the mailing list checks the policy of the
author's domain, and changes From only if the domain has a policy of
"reject" or "quarantine".

Advantage:
- Some fraction of the posts would have "From" displayed as the author
  intended it.  Depends on policies of your posters' providers.  Could
  be very large if most are academics posting from departmental
  addresses, could be very small if most are posting from personal
  Gmail addresses.

There are three possible downsides:
- People from "strict" domains complain about discrimination.
- Subscribers are confused by multiple formats.
- The list's administrative burden increases because Gmail in its
  infinite disdain for the rest of the world has decided that it does
  not apply DMARC to mail received by the rest of the world (its
  published policy is "none"), but it *does* apply it to mail Gmail ->
  list -> Gmail.  I think the most recent versions of Mailman 3 apply
  the mitigation action to Gmail implicitly, and if not it's simple to
  add "^.*@gmail\.com" to the "DMARC addresses" setting.
  The issue is that other providers may think "that's a great idea",
  and there's no way to find out they're doing it except that you get
  a lot of bouncers from subscribers using that provider.  So you have
  to monitor bounces.

 > If you think it might help to change any of those, I'll try it and
 > then roll back if it causes other problems.

That's your call.  I do recommend setting "First strip Reply-To" to
"No" to make it explicit.  All the others except "DMARC Mitigate
unconditionally" are the recommended settings for your purposes.

For "DMARC Mitigate unconditionally", I remember a lot of complaints
from AOL and Yahoo! users back in the day about "discrimination", but
I imagine people are used to DMARC mitigation by now (and of course
popular MUAs try to hide it using associations).  I've never seen much
confusion from the multiple formats, but some people just value
consistency in the user interfaces they use.  And the administrative
burden is likely to be nil unless you're really compulsive about such
things -- you just wait for bounces from a random domain to spike and
check for "From a...@ran.dom" getting bounced by "subscri...@ran.dom",
and add "^.+@ran\.dom" to the "DMARC addresses" list if and when it
happens.  Really only Gmail and Yahoo! are big enough to do this, and
most yahoo.* domains already have a "reject" policy.

 > I also think that a tweak to the T-bird MUA is a strong suspect.  The
 > affected subscriber is an old guy like me and in my experience it is also a
 > PITA for him to deal with Mozilla, his email provider (Breezeline), or any
 > other tech intermediary.
 > 
 > Mark:  Thanks for the suggestions on searching T-bird emails.  I'm going to
 > refrain from passing them on to my subscriber right now as they would
 > probably seem like another PITA.

I agree on that one, although in the long run he'd probably be a lot
happier.  Another possibility would be to keep a browser tab open on
HyperKitty's RADG page, and search authors there.  This should work
because DMARC processing takes place after archiving in the builtin
pipeline, so HyperKitty should know the author accurately.  Of course
this is suboptimal, but it may be more straightforward than messing
with MUA settings (and it works for all MUAs!)

Regards,
Yet another Steve

 > On Thu, Jul 3, 2025 at 12:06?AM Stephen J. Turnbull <st...@turnbull.jp>
 > wrote:
 > 
 > > Steve Brown via Mailman-users writes:
 > >
 > >  > "For a while now, my e-mail for this list (but not other lists)
 > >  > just shows "To RADG" from "RADG" with a "CC" showing the actual
 > >  > sender's address.
 > >
 > > It's very difficult to figure out what's going on with such an
 > > abbreviated description of what he's seeing.
 > >
 > > It may be possible to get better results with alterative settings on
 > > the list.
 > >
 > > In the settings for RADG, under "Alter Messages", what are the
 > > settings for "First strip Reply-To", "Reply goes to list", and
 > > "Explicit reply-to address"?
 > >
 > > Under "DMARC mitigations", what are the settings for "DMARC mitigation
 > > action" and "DMARC mitigate unconditionally"?
 > >
 > >  > Because some other members, including me, have had problems with
 > >  > unexpected entries in both From and To lines, I suspect that
 > >  > Mailman 3 does the DMARC enough differently
 > >
 > > The only thing I can think of that might allow other lists to have
 > > author names for other lists but not for a Mailman list is that the
 > > MUAs are parsing email addresses out of the display name (which is a
 > > horrible risk, given the flexibility that users have in setting email
 > > headers, and especially display names).  If there is no email address,
 > > then they completely ignore the content of the display name in favor
 > > of their preferred display name for the list.
 > >
 > >  > My understanding is that all of the recent posts are missing the
 > >  > poster's name, after behaving as expected for some time.  Something
 > >  > must have changed, but what is baffling me.  If you have any
 > >  > further ideas, fine, but don't waste a lot of time on this.
 > >
 > > MUA "upgrade" seems like as likely an explanation as any.  I think if
 > > you want to know details what's going on for a particular user, their
 > > MUA's support channels are the best bet.

-- 
GNU Mailman consultant (installation, migration, customization)
Sirius Open Source    https://www.siriusopensource.com/
Software systems consulting in Europe, North America, and Japan
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