Issue DMARC p=reject causes locally generated DSNs (MAILER-DAEMON) to be silently discarded

[enduser]

Server operating system version

AlmaLinux 9.4

Plesk version and microupdate number

18.0.74

On a Plesk mail server with DMARC enabled, we observed that locally generated non-delivery notifications (DSNs) are being rejected when the domain uses a strict DMARC policy:

v=DMARC1; p=reject; sp=reject;

When an outgoing email fails, Postfix generates a local DSN:

• From: MAILER-DAEMON@example.com
• Envelope sender: <>
• Recipient: local user (e.g. user@example.com)

Although example.com has a valid SPF record, the DSN is locally generated (ip=unknown, empty envelope sender) and is not evaluated against SPF, and it is not DKIM-signed. As a result, DMARC alignment fails and the DSN itself is rejected:

message discarded by a mail handler

As a result, users never receive bounce notifications, and failed outgoing emails appear to silently disappear.

This behavior is technically DMARC-compliant, but operationally problematic. Many MTAs bypass DMARC for local DSNs, or otherwise ensure bounces are delivered.

Is this behavior expected in Plesk?
Are there plans to exempt locally generated DSNs from DMARC rejection, or to provide a documented workaround?

Dec 17 03:42:36 example postfix/cleanup[1963006]: A8F2D84079: message-id=<20251216194236.A8F2D84079@example.com>
Dec 17 03:42:36 example postfix/bounce[1964920]: BEFC07AD9D: sender non-delivery notification: A8F2D84079
Dec 17 03:42:36 example postfix/qmgr[291519]: BEFC07AD9D: removed
Dec 17 03:42:36 example postfix/qmgr[291519]: A8F2D84079: from=<>, size=16465, nrcpt=1 (queue active)
Dec 17 03:42:36 example postfix-local[1965563]: A8F2D84079: from=<MAILER-DAEMON>, to=<peter@example.com>, dirname=/var/qmail/mailnames
Dec 17 03:42:36 example dmarc[1965564]: A8F2D84079: SPF record was not found in Authentication-Results
Dec 17 03:42:36 example dmarc[1965564]: A8F2D84079: DMARC: smtpdomain= maildomain=example.com mailfrom=MAILER-DAEMON@example.com stamp=1765914156 ip=unknown adkim=relaxed aspf=relaxed p=REJECT sp=REJECT pct=100 align_dkim=fail align_spf=fail spfres=unknown dkimres=unknown dmarccheck=DMARC_POLICY_REJECT dmarcstatus=STOP
Dec 17 03:42:36 example postfix-local[1965563]: A8F2D84079: dmarc: stderr: STOP
Dec 17 03:42:36 example postfix-local[1965563]: message discarded by a mail handler
Dec 17 03:42:36 example postfix/pipe[1956942]: A8F2D84079: to=<peter@example.com>, relay=plesk_virtual, delay=0.02, delays=0/0/0/0.02, dsn=2.0.0, status=sent (delivered via plesk_virtual service)
Dec 17 03:42:36 example postfix/qmgr[291519]: A8F2D84079: removed