Austin Witmer via Postfix-users:
> On Jul 22, 2024, at 5:00?PM, Wietse Venema via Postfix-users
> <postfix-users@postfix.org> wrote:
> >
> > Austin Witmer via Postfix-users:
> >>> You will need SPF, DKIM, and DMARC with 'p=reject'. If this is
> >>> an interactive list, you will need to replace list member's From:
> >>> headers with your mailing list address to satisfy DMARC.
> >>
> >> I believe I have SPF, DKIM and DMARC setup with p=reject.
> >>
> >> So the big list with 1500 members is not an interactive list and
> >> probably will just have one sending (gmail) address.
> >
> > Your server is not gmail.com, so when you send BULK mail with a
> > From: addr...@gmail.com from a non-gmail server, then that can
> > be problematic.
>
> Would it be better in your opinion to setup a dedicated address
> with a domain I own, on my server, for sending emails to a
> non-interactive list this big so that the sending address is
> "allowed" to send/relay mail through my server? That way I don't
> have the appearance of sending email on behalf of a gmail account
> from my server?
I was assuming that your Postfix server has a proper hostname with
reverse DNS that resolves to that hostname, and a domain name that
is under your control. That has been a requirement for 20 years
already. Then that would be an excellent choice for the From:
domain, and for SPF, DKIM, and DMARC policies.
> >> From what I was reading online, I thought "From munging" is not
> >> necessary if I am not modifying the subject, body or existing email
> >> headers. And thus the original senders DMARC won't be broken,
> >> right?
> >
> > That may still work with low-volume PERSONAL mail, but the rules with
> > BULK mail are different.
>
> Do you have any recommendations on how to accomplish this "From
> munging" without using something like mailman? Perhaps a milter
> of some kind?
If there is only one authorized sender, then you could pipe the
message through a script that replaces the authorized From: address
with the desired one, before feeding the message into mlmmj.
Wietse
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