no more subject prefix for xetex mailing list

[Zdenek Wagner]

Hi all,

mere rewriting of the From header will not work. There are four beasts involved:

1. SPF
2. DKIM
3. ADSP
4. DMARC

The recipient sees that MAIL FROM says that the mail came from
tug.org. It thus looks at DNS, finds the SPF record (in fact a special
type of TXT) and verifies whether the IP address is in the list of
allowed servers. This is configured correctly at tug.org hence SPF
passes.

DKIM is used to sign headers and the message. In order to verify it,
the recipient looks at the From header and uses @originating.domain to
find the public key. The DKIM headers contain the list of headers that
are signed. Thus it has nothing to do with tug.org. If you examine the
mail messages of Ulrike Fischer, you can see that they do not have
DKIM signatures but mails of Normert Preining are signed. These
persons have nothing to do with it, it is determined by the
configuratin of the mail systems of their organizations. DKIM says
what should be signed but does not say what to do if verification
fails.

ADSP is used to define what to do with maisl not passing DKIM. It is,
however, rarely used.

DMARC is a more flexible way superseding ADSP. It looks both at SPF
and DKIM and then decides what to do. Remember that DKIM as well as
DMARC are defined by the mail systems of the original senders hence
tug.org cannot do anything. In addition, it is not known which eaders
are included in the signature.

The only solution was described in my previous mail. The article
(unfortunatelly in Czech) also suggests to add an
Authentication-Results header with the results from the original mail
and sign the header by DKIM.

Zdeněk Wagner
http://ttsm.icpf.cas.cz/team/wagner.shtml
http://icebearsoft.euweb.cz

po 4. 3. 2019 v 17:28 odesílatel Mike "Pomax" Kamermans
<pomax at nihongoresources.com> napsal:
>
> On 3/3/2019 9:45 PM, Peter von Kaehne wrote:
> > Isn't the problem with DMARC around the FROM: header? I can not see how
> > altering the subject line is going to make a blind bit of difference
> > when the real problem is that the FROM header still points at the
> > author's domain.
> >
> > Peter
> >
> It is. The problem is the from address not being rewritten to the list
> mailer's address, the subject contributes nor fixes anything in that
> respect. It'd be a good idea put that [XeTeX] back in the subject line.
>
> - Pomax
>