On 2024-10-22 10:20:55 -0400, Wietse Venema via Postfix-users wrote:
> Vincent Lefevre via Postfix-users:
> [ Charset ISO-8859-1 converted... ]
> > As DMARC protection, some mailing-lists (like postfix-users)
> > rewrite the "From:" header, with at least 2 drawbacks:
> > * This breaks e-mail searching by the "From:" address.
> > * At my work, only the address is changed (without introducing
> > "via <mailing-list>"), so that this is very confusing as mail
> > appears like
> > From: Firstname Lastname <mailing-list-address>
> > and we start seeing users sending private mail to mailing-lists
> > because they did not notice that the address changed.
>
> The "via listname" part is there for a good reason - it is to prevent
> human mistakes like the one you describe.
>
> If something removes "via listname" from postfix-users messages,
> that would be a terrible mistake, and they should stop doing that.
The "via listname" is not removed, but never generated by the
mailing-list software (Sympa) at my work. I opened a ticket
to get this fixed, but there's not much reaction.
> > I was wondering whether I could ask postfix to revert the "From:"
> > header back to the original value, just before the local delivery,
> > at least for lists that keep the original address in some other
> > header ("X-MailFrom:" for postfix-users, "X-Original-From:" for
> > some mailing-lists...). Any idea?
>
> No, but you're welcome to contribute a content filter (Milter) that
> does this. A Milter can be implemented in many programming languages,
> and would work like this:
>
> - Look at each SMFIC_RCPT event and see if the recipient domain is
> local (a configurable list of domains).
Looking at the recipient domain is not sufficient, because some
addresses are forwarded via a virtual_alias map (and the "From:"
must not be changed in such cases). So I was wondering whether the
header could be rewritten in some step after the look at this table.
BTW, I don't understand where this table occurs at
https://www.postfix.org/OVERVIEW.html (I initially thought
about virtual(8), but this is only the delivery agent).
On 2024-10-23 00:35:54 +0200, Steffen Nurpmeso via Postfix-users wrote:
> Wietse Venema via Postfix-users wrote in
> <[email protected]>:
[...]
> |- Look at each SMFIC_HEADER event, and see if it is an "X-MailFrom:"
> |or "X-Original-From:" header (a configurable list of labels).
>
> That is what Author: is meant for btw.
>
> |- When receiving an SMFIC_EOH (end of headers) event, if there was
> |no "From: XXX via YYY" header, replace From: with content from
> |"X-MailFrom:" or "X-Original-From:".
>
> In general it is surely only a user interface question if Author:
> would finally be adopted.
Probably not a user interface issue. If mail client starts showing
the "Author:" address instead of "From:", DMARC/SPF would probably
evolve to also ban a different domain in "Author:" to protect the
recipient against domain spoofing. :-(
--
Vincent Lefèvre <[email protected]> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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