On Sat, 2023-08-19 at 19:10 +0300, Victor Ustugov via Exim-users wrote:
> Jeremy Harris via Exim-users wrote on 19.08.2023 18:37:
> > On 19/08/2023 16:29, Victor Ustugov via Exim-users wrote:
> > > But
> > > this won't work if there is no Message-ID header in the original
> > > email.
> >
> > You can safely block any external-source messages lacking a
> > Message-ID header (local ones, where you're being an MSA,
> > not so; some MUAs are dumb and the MSA has to fix then up.
> > Exim does that).
> >
> > RFC 5322 only lists this as a SHOULD (section 3.8.4) -
> > but I see it as spamsign.
>
> I can't block emails that don't contain Message-Id headers. You can't
> even imagine how many emails that do not meet the requirements of the
> RFC come from official organizations, suppliers, buyers.
>
> For example, emails from noreply@??? with a DMARC Aggregate
> Report have a Message-ID header. But it doesn't contain angle
> brackets.
>
> Thus, the absence of the Message-ID header or the incorrect format of
> the Message-ID header are not reliable criteria for refusing to
> deliver a message.
>
FWIW, Google treat it as a MUST and (at least some of the time) refuse
such messages at SMTP time.
Regards,
Adam
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