Issue Some incoming spam emails don't have "X-Spam-" headers and delivered to inbox

[tajt02]

Hello,

since ~2 days I get spam emails with subject "invoice" several times a day. I wonder why, because usually my Plesk SpamAssassin moves them automatically into spam folder.

So I checked the headers to find out if I need to change the value. But these emails have no X-Spam-headers!!

Usually I have:
- X-Spam-Checker-Version
- X-Spam-Level
- X-Spam-Status

But these spam/virus emails have nothing of that...

The same on another server where I get the same spam mails on my other domains.

Why?

Here's an example header of one of these emails:

From - Wed Jul 20 22:37:44 2016
X-Account-Key: account8
X-UIDL: UID1706-1414333530
X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
X-Mozilla-Keys:
Return-Path: <Crawford.834@static.vnpt.vn>
X-Original-To: info@xxx.com
Delivered-To: info@yyy.com
Received: from static.vnpt.vn (unknown [14.161.37.4])
by my-mta-domain.com (Postfix) with ESMTP id A975A11201BB
for <info@xxx.com>; Wed, 20 Jul 2016 22:29:17 +0200 (CEST)
To: info@xxx.com
From: "Allyson Crawford" <Crawford.834@static.vnpt.vn>
Subject: invoice
Organization: ANGLO ASIAN MINING PLC
Message-ID: <044efea4-b0b0-8823-xxxxx@xxx.com>
Date: Thu, 21 Jul 2016 03:29:07 +0700
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0)
Gecko/20100101 Thunderbird/45.1.0
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="------------F21743C964AC2DF30F594DC3"

This is a multi-part message in MIME format.
--------------F21743C964AC2DF30F594DC3
Content-Type: multipart/alternative;
boundary="------------10C0CC2C14C3D11797ABBDF5"


--------------10C0CC2C14C3D11797ABBDF5
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit