On Wed, 1 May 2024, Jeremy Harris via Exim-users wrote:
> On 01/05/2024 22:42, The Doctor via Exim-users wrote:
>> What is external forwarding?
>>
>> Sound like something scary.
>
> My *guess* is:
>
> You mailed person A.
... or someone pretending to be you mailed A ...
> A has their mails configured, at the MX for A,
> to be forwarded to B. You don't have control over that
> configuration;
> it is entirely A's choice. He wanted it to be done.
>
> But you have configured your system, probably in "SPF" terms,
> you
> say "any messages claiming to be from me *must* be be sent by
> *my* system.
> Any messages being sent by any other system are invalid, and
> should be rejected."
>
> The message is being sent onwards by A's MX to B's MX. it is
> being sent by
> A's MX, as far as B's MX is concerned.
>
> B's MX implements SPF, and does what you claim you wanted. It
> rejects the
> message, since the message did not arrive at that host directly
> from your MX.
>
>
>
> And thus, a traditional and useful feature of email handling
> has been broken.
> --
> Cheers,
> Jeremy
>
>
> --
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--
Andrew C. Aitchison Kendal, UK
andrew@???
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