title: Email header with multiple received fields: How can this happen and can this be used to fight SPAM
body: <p>I often receive fishing /SPAM emails with multiple received fields.</p>
  
  <p>First, I'd like to understand how one email header can have more than one received field.</p>
  
  <p>Second, I'd like to know if I can use this to fight SPAM.</p>
  
  <p>Here is an example:</p>
  
  <pre>
  
      Return-Path: 
      X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on myhosting.com
      X-Spam-Level: 
      X-Spam-Status: No, score=0.0 required=3.5 tests=HTML_MESSAGE autolearn=ham
          version=3.3.2
      X-Spam-ASN: 
      X-Original-To: my@email.rs
      Delivered-To: my@email.rs
      Received: from posta.abak.si (posta.abak.si [84.255.212.92])
          by myhosting.com (Postfix) with ESMTPS id 522CA80DC8
          for ; Wed, 8 May 2019 14:31:59 +0200 (CEST)
      Authentication-Results: myhosting.com;
          dmarc=none (p=NONE sp=NONE) smtp.from=mk.kema-on.net header.from=mk.kema-on.net;
          spf=none (sender IP is 84.255.212.92) smtp.mailfrom=dime.mitreski@mk.kema-on.net smtp.helo=posta.abak.si
      Received-SPF: none (myhosting.com: no valid SPF record)
      Received: from localhost (localhost [127.0.0.1])
          by posta.abak.si (Postfix) with ESMTP id 2C09E1E6A7D7
          for ; Wed, 8 May 2019 14:35:06 +0200 (CEST)
      Received: from posta.abak.si ([127.0.0.1])
          by localhost (posta.abak.si [127.0.0.1]) (amavisd-new, port 10032)
          with ESMTP id dw1MvahvfmXL for ;
          Wed, 8 May 2019 14:35:05 +0200 (CEST)
      Received: from localhost (localhost [127.0.0.1])
          by posta.abak.si (Postfix) with ESMTP id EB2B21E6A3C6
          for ; Wed, 8 May 2019 14:30:12 +0200 (CEST)
      X-Virus-Scanned: amavisd-new at posta.abak.si
      Received: from posta.abak.si ([127.0.0.1])
          by localhost (posta.abak.si [127.0.0.1]) (amavisd-new, port 10026)
          with ESMTP id luUYSdWOdHLE for ;
          Wed, 8 May 2019 14:30:12 +0200 (CEST)
      Received: from IP-129-13.dataclub.eu (unknown [84.38.129.13])
          by posta.abak.si (Postfix) with ESMTPA id B18CD1E6A7A6
          for ; Wed, 8 May 2019 14:25:39 +0200 (CEST)
      Content-Type: multipart/alternative; boundary="===============0253676305=="
      MIME-Version: 1.0
      Subject: Warning: you have (3) Undelivered messesges
      To: my@email.rs
      From: "Webmaster" 
      Date: Wed, 08 May 2019 15:25:37 +0300
      Message-Id: 
      Message Body
  
  </pre>