Re: resending bounces: DKIM and Message-ID:

[Eric Abrahamsen <eric@ericabrahamsen.net>]

Greg Troxel <gdt@lexort.com> writes:

> I found a behavior problem that I think is a bug in both gnus and
> opendkim.  Headers that are supposed to be added by the originating MTA
> are not removed, so the resent message has odd content: duplicate DKIM
> header, and the same Message-ID:
>
> My system in NetBSD 9 amd64 with emacs 28.2, but I don't think that's
> particularly important.
>
> Reproduction Recipe:
>
>   - send a message to a mailing list that you are not subscribed to, so
>     that it will bounce, and CC: an actual person
>   - subscribe to the list and confirm
>   - In the summary at the bounce, S D b (gnus-summary-resend-bounced-mail)
>   - In the resulting message buffer, C-c C-c (realizing or not realizing
>     that the actual person will get a second copy)
>
> This seems to me to be a normal sequence of events, and I'm here because
> it actually happened.  It was a discussion of DKIM/DMARC configuration
> for mailman, so the person in the CC: got two copies and actually
> noticed that there were two DKIM headers from my domain.
>
>
> The problem is that the message that is sent has two DKIM headers.  This
> is because the one that was added by the MTA on the way to the
> mailinglist is present because it was in the bounce, and then opendkim
> added a new one, because it just adds.
>
> But also, the Message-ID: was generated for the first message, and the
> that is reused.  That seems also like a bug.
> 
> The proposal is to fix this by:
>
>   * in gnus
>     - adding a list of headers which should be removed from bounce
>       messages when doing gnus-summary-resend-bounced-mail

I believe this is called `message-ignored-bounced-headers'! It does not
currently include DKIM-Signature, but maybe it should. I haven't
actually tested this, but looking at the code I believe it should take
effect in this situation.

>     - set the list to Message-ID and DKIM-Signature to start with

This is deeper in the protocol weeds than I usually go, so this is a bit
tentative, but I will note that there's a separate
`gnus-summary-resend-message-edit' command, which will not preserve the
Message-ID header. I think there's an argument to be made that, if
you're re-sending the bounced the message, it is in fact the same
message over again. If you're changing the "To:" or other headers, on
the other hand, that sounds like a new message, and you should be using
"S D e" instead.

What do you think?

Eric