Re: Mail delivery from Postfix to remote IMAP

[Steffen Nurpmeso <steffen%sdaoden.eu@localhost>]

Rhialto wrote in
 <Zia3PK5ejTV-GbR5%falu.nl@localhost>:
 |On Mon 22 Apr 2024 at 11:20:59 -0700, Greg A. Woods wrote:
 |> Just keep doing what you're doing.  Anything else _is_ more roundabout.
 |> Why complicate things?  SMTP forwarding is the way to keep it working!
 |
 |I agree with you in spirit. Plain forwarding is a basic feature of SMTP.
 |
 |BUT.
 |
 |The trouble with plain forwarding is that my mail server's domain name
 |doesn't match the domain name in the From: header, and doesn't match the
 |envelope FROM domain, and it doesn't match the SPF policy of the sender
 |domain etc etc. Those are things that are checked by DKIM/DMARC/SPF.
 |
 |And you can't change the From: header because that is changing the mail
 |(and invalidates the DKIM signature), and neither can you change the
 |envelope FROM address because bounces (as far as they happen) won't work.
 |
 |> Of course fixing your mail server to do proper DKIM, or even just
 |> futzing with SPF (and PTR) records enough to get normal SMTP port#25
 |> through, i.e. without heavier AUTH and use of the submission service,
 |> would be even simpler.  I've done the latter, and hope to do more with
 |> DKIM soon (but _NOT_ with the milter mess!).
 |
 |Unfortunately DKIM is designed to break forwarding... I can't think of a

That is SPF, which does not survive more than one hop.

 |way to change an email message to make it DKIM-compliant. Mailing lists

That is DMARC.  (DKIM default is to ignore failures.)

 |can get away with changing the From: header to something like
 |"list%example.org@localhost (Rhialto via Example-List)" (and that's already an
 |ugly thing to do) but that's not an option for individual mails.

For forwarding what you (UNFORTUNATELY) need is SRS aka
https://github.com/roehling/postsrsd.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)