Note: the appropriate list for MM 3 is [email protected]

On 10/24/24 04:13, Ralf Hildebrandt via Mailman-Users wrote:
Hi!

We're running [email protected] and we're encountering an odd
problem: A system is sending mailing list messages that were posted on
[email protected] BACK to [email protected]

And these mails simply pass moderation (which is set to the following):
Default action to take when a member posts to the list: Default processing
Default action to take when a non-member posts to the list: discard (no 
notification)

The headers of the mail (which I put on hold, based on the IP of the
sending system):

Date: Thu, 24 Oct 2024 11:13:01 +0200
To: [email protected]
Message-ID: <[email protected]>
In-Reply-To: <[email protected]>
X-MailFrom: [email protected]
X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency;
  loop; banned-address; member-moderation;
  header-match-postfix-users.postfix.org-0; nonmember-moderation;
  administrivia; implicit-dest; max-recipients; max-size; news-moderation;
  no-subject; digests; suspicious-header
X-Mailman-Version: 3.3.9
Precedence: list
Content-Type: text/plain; charset="us-ascii"
Message-ID-Hash: Z6I2WZCEBC6PUKLVOEVAW3ZU2CDR47AW
X-Message-ID-Hash: Z6I2WZCEBC6PUKLVOEVAW3ZU2CDR47AW
X-MailFrom: [email protected]
X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency;
  loop; banned-address; member-moderation;
  header-match-postfix-users.postfix.org-0; nonmember-moderation;
  administrivia; implicit-dest; max-recipients; max-size; news-moderation;
  no-subject; digests; suspicious-header
Subject: 
=?utf-8?B?W+WklumDqOmCruS7tl1bcGZ4XSBb5aSW6YOo6YKu5Lu2XVvlpJbpg6jpgq7ku7ZdUmU6IE9wZW5TU0wgY29tcGlsZSB2cy4gcnVudGltZSB2ZXJzaW9uIHdhcm5pbmc=?=
From: Geert Hendrickx via Postfix-users via Postfix-users
  <[email protected]>
Reply-To: Geert Hendrickx <[email protected]>,
  Geert Hendrickx via Postfix-users <[email protected]>

So, it's the mail from "Geert Hendrickx" being resent from
[email protected] -- the headers have both

"X-MailFrom: [email protected]" (not a member of the list) and

I think this is the envelope sender of this message

"X-MailFrom: [email protected]" (definitely a member of the list)

and I think this is the envelope sender of the original message that was bounced back.

Why is the mail being accepted?

Because [email protected] is in the list returned by mailman.email.message.Message.senders and is a list member presumably with moderation_action Default Processing. In this case it is because [email protected] is in Reply-To:.

If I am correct about 5the envelope sender, the full list returned by the senders method is
```
['[email protected]', '[email protected]', '[email protected]']
```
being respectively From:, envelope sender and Reply-To:

From: doesn't look right (since it says "[email protected]")

We're currently stopping these mails, but I think mm3 is not acting
correctly here (unless we're missing something)

List membership is determined by much more than From:. See https://gitlab.com/mailman/mailman/-/blob/master/src/mailman/email/message.py?ref_type=heads#L87-L107

If you want list membership to be determined solely by From:, you need to put
```
sender_headers: from
```
in the `[mailman]` section of mailman.cfg. If you just want to drop Reply-To, you can use
```
sender_headers: from from_ sender
```

--
Mark Sapiro <[email protected]>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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