Issue Bug: “Mail for Non-Existent Users → Reject” not applying reject_unlisted_recipient in Postfix (Plesk 18.0.72 / Debian 12)

[Betafer]

Server operating system version

Debian 12

Plesk version and microupdate number

18.0.72 Update #2

Hello,

I have found a bug in Plesk Obsidian 18.0.72 Update #2 "(and below)" running on Debian 12.

Steps to reproduce:​

1. Go to Mail → Mail Settings → Mail for Non-Existent Users.
2. Select Reject.
3. Expectation: Plesk should configure Postfix with
   
   smtpd_recipient_restrictions = ... reject_unlisted_recipient ...
   so that messages sent to non-existent mailboxes are rejected at SMTP time.
4. Actual result: The directive reject_unlisted_recipient is missing in /etc/postfix/main.cf.
   Postfix accepts emails for non-existent recipients, which later generate bounce messages (backscatter).

Workaround:​

Manually editing /etc/postfix/main.cf and adding:



smtpd_recipient_restrictions = reject_unlisted_recipient, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination


fixes the issue.
Alternatively, placing an override in /etc/postfix/conf.d/ ensures persistence after updates.

Impact:​

• Causes backscatter spam.
• Breaks expected functionality: GUI setting “Reject” does not translate to Postfix configuration.

Environment:​

• Plesk Obsidian 18.0.72 Update #2
• Debian 12 (bookworm)
• Mail server: Postfix

---

Request:​

Please investigate and fix the inconsistency between the Plesk GUI setting Mail for Non-Existent Users → Reject and the actual Postfix configuration.


Thank you,
Betafer.it