On 10.05.25 13:32, Ken Biggs via Postfix-users wrote:
So continuing the saga ... digging into /etc/postfix/header_checks I found
a revision I made back in January to try to keep our outgoing email from
having headers with the IP address of the email client that sent the email
to the server and maybe keep Gmail from marking our outgoing email as
SPAM.
/^Received:.*with ESMTPSA/ IGNORE
/^X-Originating-IP:/ IGNORE
/^X-Mailer:/ IGNORE
/^Mime-Version:/ IGNORE
These should not be used globally but only at submission level.
This can be achieved by using separate postfix instance for submitted mail
- I don't see possibility of configuring separate cleanup instance for smtpd
http://www.postfix.org/MULTI_INSTANCE_README.html
If I comment that out and add
mime_header_checks = regexp:/etc/postfix/header_checks
header_checks = regexp:/etc/postfix/header_checks
back into main.cf DKIM still appears to work properly. So, looks like I
probably broke it back in January. Gack ... apparently I didn't test that
revision correctly and it was rewriting incoming email headers.
according to rest of discussion, dropping Mime-Version: was the culprit and
you should never to that (you break mime mail).
On May 10, 2025 5:57:34 PM UTC, Dan Mahoney via Postfix-users
<postfix-users@postfix.org> wrote:
Mime-version was listed as a signed header but was absent.
I suspect his header checks cleaned that out.
Note that having a header listed in the H equals list, but having that header
be absent is legal, but I don’t know why the signing software would say it’s
signing that header when it’s not there.
On May 10, 2025, at 1:06 PM, Scott Kitterman via Postfix-users
<postfix-users@postfix.org> wrote:
Generically (probably not relevant here), 'signing' a non-existent header field
will cause the signature verification to fail if one is later added. There may
be times when that's desirable.
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