Re: BUG #18822: mailing lists reject mails due to DKIM-signature

On 22.02.25 18:25, Tom Lane wrote:
> Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> writes:
>> On 22.02.25 17:56, Matthias Apitz wrote:
>>> Have you read what the RFC 6576 specifies about exactly this case?
>
>> we are a forwarder that (in the case of a List-* header) NEEDS to modify
>> the message so we cannot forward it without breaking.
>
> Yeah. Regardless of what may be written in the RFC, there are only
> these possibilities when the mailing list forwarder receives a
> message like this:
>
> 1. Add the PG list headers, don't touch the DKIM header, forward.
> Most modern recipients will reject the result as spam because it
> fails DKIM checks.
>
> 2. Don't add the PG list headers, don't touch the DKIM header,
> forward. Many list recipients will discard or at least
> misclassify the result for lack of PG list headers.
>
> 3. Add the PG list headers, discard the DKIM header, forward.
> This may well end up marked as spam too, and it's certainly
> not complying with the intent of DKIM.
>
> 4. Reject the message.
>
> To the extent that including List-* in a DKIM signature has any
> real-world use, it is precisely to disavow the message if it's
> forwarded by a mailing list.
>
> The short answer here is that your ISP are fools, or else are
> intentionally preventing their users from participating in
> mailing lists.

exactly (and thanks for the roundup of our "non"-options).

There is basically nothing we can do about that other than recommending
a different ISP or one of the myriads of free mail providers out there
that get this right.

Stefan