From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
cc: Matthias Apitz <gurucubano@googlemail.com>,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18822: mailing lists reject mails due to DKIM-signature
In-reply-to: <c5be0df1-8953-4531-81dd-9395082883d9@kaltenbrunner.cc>
References: <18822-25d115fe42e642c2@postgresql.org>
 <7d1cf55f-4228-49d8-8066-cf96deab8ad3@kaltenbrunner.cc>
 <CAHzebO8PGHFB8e7_5bYc=HefWo5rr7dhuMLg-zmGLmaRWxW5aQ@mail.gmail.com>
 <c5be0df1-8953-4531-81dd-9395082883d9@kaltenbrunner.cc>
Comments: In-reply-to Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
	message dated "Sat, 22 Feb 2025 18:14:17 +0100"
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Date: Sat, 22 Feb 2025 12:25:57 -0500
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Stefan Kaltenbrunner <stefan@kaltenbrunner.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.

			regards, tom lane