[BUG] delivery status notifications should not get BROKEN_HEADERS

[kasak87]

Describe the bug
When normal delivery status notifications is cheked, they always get BROKEN_HEADERS symbol, because of empty "mail from" in envelope.

Steps to Reproduce

1. Use default rspamd config.
2. Just wait for any delivery status notification.

Expected behavior
Empty "mail from" header is not "broken", sometimes it should be empty.

DSNs should have empty "mail from" as described in RFC3464 https://datatracker.ietf.org/doc/html/rfc3464

The envelope sender address of the DSN SHOULD be chosen to ensure that no delivery status reports will be issued in response to the DSN itself, and MUST be chosen so that DSNs will not generate mail loops. Whenever an SMTP transaction is used to send a DSN, the MAIL FROM command MUST use a NULL return address, i.e., "MAIL FROM:<>".

Versions

Rspamd daemon version 3.0 from OpenBSD 7.0 packages.
Same behavior were in 2.7 from OpenBSD 6.9

[vstakhov]

The standard explains envelope from and not the From header. From header must be valid in all cases. From the same RFC:

The From field of the message header of the DSN SHOULD contain the
   address of a human who is responsible for maintaining the mail system
   at the Reporting MTA site (e.g., Postmaster), so that a reply to the
   DSN will reach that person. 

So there is nothing to fix on Rspamd side.

[kasak87]

The standard explains envelope from and not the From header. From header must be valid in all cases. From the same RFC:

The From field of the message header of the DSN SHOULD contain the
   address of a human who is responsible for maintaining the mail system
   at the Reporting MTA site (e.g., Postmaster), so that a reply to the
   DSN will reach that person. 

So there is nothing to fix on Rspamd side.

exactly! Here is sample message with filled "From" and empty "mail from"

Return-Path: <>
Received: from mail.tvema.ru (LHLO mail.tvema.ru) (212.233.112.11) by
mail.tvema.ru with LMTP; Thu, 18 Nov 2021 15:20:36 +0300 (MSK)
Received: from localhost (localhost [127.0.0.1])
by mail.tvema.ru (Postfix) with ESMTP id 5A1CD426358D
for fedorova@tvema.ru; Thu, 18 Nov 2021 15:20:36 +0300 (MSK)
Received: from mail.tvema.ru ([127.0.0.1])
by localhost (mail.tvema.ru [127.0.0.1]) (amavisd-new, port 10026)
with ESMTP id gC8Pb9Z2IuhW for fedorova@tvema.ru;
Thu, 18 Nov 2021 15:20:36 +0300 (MSK)
Received: from gater.ugr.tvema.ru (gater.ugr.tvema.ru [172.16.0.1])
by mail.tvema.ru (Postfix) with ESMTPS id 33665426351A
for fedorova@tvema.ru; Thu, 18 Nov 2021 15:20:36 +0300 (MSK)
X-Spam: yes
X-Spam-Score: 9.899999 / 15
X-Spam-Status: Yes, score=9.900 required=15.000
tests=[ARC_NA=0.000, ARC_SIGNED=0.000, ASN=0.000, BAYES_SPAM=5.100
BOUNCE=-0.100, BROKEN_HEADERS=10.000, DMARC_POLICY_ALLOW=-0.500
FROM_NO_DN=0.000, GREYLIST=0.000, MIME_GOOD=-0.100, MIME_TRACE=0.000
NEURAL_SPAM=0.000, ONCE_RECEIVED=0.100, PREVIOUSLY_DELIVERED=0.000
RCPT_COUNT_ONE=0.000, RCVD_COUNT_ONE=0.000, RCVD_IN_DNSWL_MED=-0.400
RCVD_TLS_ALL=0.000, REPLY=-4.000, R_DKIM_NA=0.000, R_SPF_ALLOW=-0.200
TO_DN_NONE=0.000, TO_MATCH_ENVRCPT_ALL=0.000]
X-Spam-Flag: YES
Received: from ul-edge.skbkontur.ru (ul-edge.skbkontur.ru [46.17.201.48])
by tvema.ru (OpenSMTPD) with ESMTPS id 2b8ba5af (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256:NO)
for fedorova@tvema.ru;
Thu, 18 Nov 2021 15:20:35 +0300 (MSK)
MIME-Version: 1.0
From: postmaster@skbkontur.ru
To: fedorova@tvema.ru

[vstakhov]

I'm not sure it happens because of from header. Could your please share any of the problematic messages with me using my personal email?

[kasak87]

I'm not sure it happens because of from header. Could your please share any of the problematic messages with me using my personal email?

sent a couple. Thank's!

[vstakhov]

Hum, you MTA sends an empty string for DSN instead of <>. I have added a workaround on Rspamd side but it looks weird.

[kasak87]

Thank you! I can assure you, this is not only my mta work like this, there are tons of similar mails, as you can see, bayes have autolearned from this messages and now consider them all as spam.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[kasak87]

no problems with new rspamd 3.2 in OpenBSD 7.1!
Thanks a lot!