I have the same error on several servers (Plesk Obsidian 18.0.62)
Mail for unknown emailaddress of any domain on the server get to the Email registered in the Admin Profile (in my case an external email address).
These are no sendmail mails, normal mails coming from outside. Example here:
Mail wants to get the mail first to the unknown address, after redirecting to
unknownaddress@localhost.localdomain and then getting to the Administrator Emailaddress
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From - Wed Aug 21 08:25:43 2024
X-Account-Key: account1
X-UIDL: UID250879-1582818771
X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
X-Mozilla-Keys:
Return-Path: <
info@info.com>
X-Original-To: EMAILADDRESSOFPLESKADMIN
Delivered-To: EMAILADDRESSOFPLESKADMIN
Received: from PLESKSERVER (PLESKSERVER [PLESKIP])
by MYMAILSERVEROUTSIDEPLESK (Postfix) with ESMTPS id 4FA6B1246C4
for <EMAILADDRESSOFPLESKADMIN>; Wed, 21 Aug 2024 08:17:18 +0200 (CEST)
Received: by PLESKSERVER (Postfix)
id DB20A18009F; Wed, 21 Aug 2024 08:17:17 +0200 (CEST)
Delivered-To:
UNKNOWNADDRESS@localhost.localdomain
Received: from babakasabaka.ru (unknown [103.109.100.173])
byPLESKSERVER (Postfix) with ESMTPS id E7D1518002D
for <UNKNOWNADDRESS@DOMAINONPLESKSERVER>; Wed, 21 Aug 2024 08:17:13 +0200 (CEST)
Authentication-Results: PLESKSERVER;
spf=softfail (sender IP is 103.109.100.173) smtp.mailfrom=
info@info.com smtp.helo=babakasabaka.ru
Received-SPF: softfail (PLESKSERVER: transitioning domain of info.com does not designate 103.109.100.173 as permitted sender) client-ip=103.109.100.173; envelope-from=
info@info.com; helo=babakasabaka.ru;
Message-ID: <
25b9f259d3d15a51760c45ee5ffbd0ce27ab57@info.com>
From: Serenity Cantu <
info@info.com>
To: UNKNOWNADDRESS@DOMAINONPLESKSERVER
Subject: Your bonus
Date: Wed, 21 Aug 2024 08:17:02 +0300
MIME-Version: 1.0
Content-Type: multipart/related; boundary="09a394f9ac68469dbe1418d326f71644d8"
.........