Why do emails from my mail server end up in spam for mail.ru recipients?

Question

Mail server

Hello! I ran into an unexpected problem. Raised the mail server on Postfix + Dovecot. Configured dkim spf dmarc. In the local network, as well as on yandex, gmail, etc. mailboxes, mail leaves and arrives without problems. The problem arose at all users using Outlook. When sending emails via Outlook to mail.ru mailboxes, they end up in spam. With other mail clients, this problem is not observed. Everyone has different versions of Outlook 2010, 2013, 2016. Here are the service headers of two identical letters sent from the same mailbox, but from different clients (Outlook 2016 and Thunderbird). The Outlook letter has the heading x-mras probable_spam, Thunderbird x-mras OK. Tell me where to dig?

Answer 1

The problem was solved (surprisingly) by writing a ticket to [email protected] Sent the body of the letter to eml and headers. After 3 hours, a letter came that the problem was fixed, though the reason could not be found out. Judging by the headlines, the problem is somehow related to the mysterious X-Magic about which I could not find any information on the net. I am attaching, for comparison, the headers of the same letter, but after the problem was fixed.

OK mail

Delivered-To: [email protected]
Return-path: <[email protected]>
Received-SPF: pass (mx216.i.mail.ru: domain of vniiprh.ru designates 212.13.30.226 as permitted sender) client-ip=212.13.30.226; [email protected]; helo=mail.vniiprh.ru;
Received: from mail.vniiprh.ru ([212.13.30.226]:43052)
  by mx216.i.mail.ru with esmtp (envelope-from <[email protected]>)
  id 1fiIhs-0002hn-Up
  for [email protected]; Wed, 25 Jul 2018 15:15:54 +0300
Received: from DeaDBeaTPC (unknown [192.168.0.21])
  (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
  (No client certificate requested)
  by mail.vniiprh.ru (Postfix) with ESMTPSA id ED80D206AC64
  for <[email protected]>; Wed, 25 Jul 2018 15:15:49 +0300 (MSK)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vniiprh.ru; s=mail;
  t=1532520950; h=from:from:sender:reply-to:subject:subject:date:date:
   message-id:message-id:to:to:cc:mime-version:mime-version:
   content-type:content-type:content-transfer-encoding:in-reply-to:
   references; bh=ez8h/mA6CdwaP2K+YlKLZbqRozKt62gG9D29A/gQIYA=;
  b=pNwBewWAteAsjdKMz1U0O9zbJeTocVulK3uycXhsh2jVchjEOgiXfuV5nsuYcyA10u8G0H
  TpxtFGTRxUH8B3Cy9cZ7RkEMTgS3i+kyxI1tghtrcU//yPiuigzMeHjbzh8Zxp7F16/SyE
  dE1AxVaMsOeV7bA+OIBetIsEO5RXxZU=
From: "admin" <[email protected]>
To: <[email protected]>
Subject: test
Date: Wed, 25 Jul 2018 15:15:23 +0300
Message-ID: <[email protected]>
MIME-Version: 1.0
Content-Type: multipart/alternative;
  boundary="----=_NextPart_000_09AD_01D4242A.4F680330"
X-Mailer: Microsoft Outlook 16.0
Content-Language: ru
Thread-Index: AdQkERkUFruDmmlbSq6moC+CyCmX9g==
X-6b629377: 1
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
X-DMARC-Policy: quarantine
X-DMARC-Result: pass
X-Mailru-Dmarc-Auth: dmarc=pass [email protected]
X-Mras: OK
X-Spam: undefined
Authentication-Results: mxs.mail.ru; spf=pass (mx216.i.mail.ru: domain of vniiprh.ru designates 212.13.30.226 as permitted sender) [email protected] smtp.helo=mail.vniiprh.ru;
   dkim=pass header.d=vniiprh.ru; dmarc=pass [email protected]
X-Mailru-Intl-Transport: d,c9393b0

X-Magic is missing here, as in the letter from Thunderbird

Answer 2

Emails from Outlook end up in spam on systems protected by Kaspersky antispam
.