Spotted during a debug session with @ptdradmin at Brussels:
Aug 22 16:44:01 hervil postfix/submission/smtpd[84108]: NOQUEUE: reject: RCPT from docker-002.nasqueron.org[51.255.124.9]: 550 5.1.1 <notifications-noreply@devcentral.nasqueron.org>: Recipient address rejected: User unknown in virtual mailbox table; from=<notifications-noreply@devcentral.nasqueron.org> to=<notifications-noreply@devcentral.nasqueron.org> proto=ESMTP helo=<localhost.localdomain> sasl_method=LOGIN sasl_username=devcentral@nasqueron.org
Phabricator sends mail to itself to the no-reply address, with valid users in CC.
Those mails are discard by Postfix.