--- Begin Message ---
Hi Giorgio,
On Wed, Dec 27, 2023 at 10:51:51AM +0100, Giorgio Bonfiglio via uknof wrote:
> this stuff became RFC and not recently… Shouldn’t a well respected
> tech list be configured in a way which doesn’t break validation?
How DKIM works is in an RFC, but how to operationally use it isn't,
so much. It's not universally agreed that mailing list operators
SHOULD (or MUST) NOT change the subject lines as the emails go
through. Not every mailing list operator believes that, and there is
no standard to tell them they are right/wrong.
On top of that, this has gone through different fashions as time
went on:
First¹ wave: we don't stick tags in the subject or change the
Reply-To; we are all adults here with competent MUAs and we can all
filter email based on headers.
Second wave: Not everyone has access to good MUAs so we'll add
subject tags to make it easier for people to filter either by
software or brain alone. And we'll set a Reply-To because we want
all discussion to go back onto the list.
Third wave: If you change the subject of an email you'll break DKIM,
so either do it and also change From address to be the list, take
responsibility and DKIM sign as the mailing list; or don't change
anything and let DKIM remain intact.
I have no idea if uknof ended up the way it is through luck, habit
or design, but there is no RFC comment on what should be done, only
what should happen in each case.
So you're asking on the basis of it being obvious to you, but it's
not obvious. Nevertheless it's a decision to make for mailing lists
in the DKIM and DMARC era.
Personally I'd replace mailing lists with Discourse and the problem
is gone.
Thanks,
Andy
¹ I appreciate that some readers may now be shouting, "first wave?
FIRST!? I was participating in technical group discussions over
UUCP" at their screen. But you know what I mean. 😀
--- End Message ---
