I'm having a problem where some user's of my web site complains they're receiving empty e-mail messages. After comparing the content and e-mail header of their e-mails with the ones I get I'm leaning onto the conclusion that their mail server somehow changes the content. Spam filter or virus filter maybe? I can't pinpoint that any of them exists through their mail header though.

I've tested on GMail and Exchange 2010 with more-or-less the same header results.

Delivered-To: my.email@gmail.com
Received: by with SMTP id p4csp162755oex;
        Wed, 16 Jan 2013 05:01:10 -0800 (PST)
X-Received: by with SMTP id a6mr591545lbg.117.1358341269727;
        Wed, 16 Jan 2013 05:01:09 -0800 (PST)
Return-Path: <their@email.com>
Received: from sending.mail.server.com (sending.mail.server.com [])
        by mx.google.com with ESMTP id n2si11385089lbk.106.2013.;
        Wed, 16 Jan 2013 05:01:09 -0800 (PST)
Received-SPF: neutral (google.com: is neither permitted nor denied by best guess record for domain of noreply@nibeuplink.com) client-ip=;
Authentication-Results: mx.google.com;
       spf=neutral (google.com: is neither permitted nor denied by best guess record for domain of noreply@nibeuplink.com) smtp.mail=noreply@nibeuplink.com
X-AuditID: 0a0201f8-b7f646d000000e46-26-50f6a494a5ce
Received: from webserver (Unknown_Domain [])
  by sending.mail.server.com (Corporate mail) with SMTP id A2.B0.03654.494A6F05; Wed, 16 Jan 2013 14:01:08 +0100 (CET)
Message-ID: <B2.B0.03654.494A6F05@sending.mail.server.com>
MIME-Version: 1.0
From: "Web Service"
To: my.email@gmail.com
Date: 16 Jan 2013 14:01:07 +0100
Subject: The Subject
Content-Type: multipart/alternative;

Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable

The user seems to be using Exchange 2003 as a server and the message they receive uses a different boundary than my server seems to be generating. Therefore I think the e-mail has been reubilt somewhere at the user's side and at that time lost some of its content.

x-mimeole: Produced By Microsoft Exchange V6.5
Received: from their.last.mail.server.net ([]) by
 computer.corporate.net with Microsoft SMTPSVC(6.0.3790.4675); Tue, 15 Jan
 2013 13:22:30 +0200
Content-Type: multipart/alternative;
Received: from another.of.their.mail.servers.net ([]) by
 their.last.mail.server.net with Microsoft SMTPSVC(6.0.3790.4675); Tue, 15 Jan
 2013 12:22:30 +0100
Received: from mail.server.net (mumrelp001.nsn-inter.net
 []) by another.of.their.mail.servers.net (
 with ESMTP id r0FBMSDH026761 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA
 bits=256 verify=OK) for <receiving.mail@address.com>; Tue, 15 Jan 2013
 12:22:28 +0100
Received: from sending.mail.server.com (sending.mail.server.com []) by
 mail.server.net (8.13.8/8.13.8) with ESMTP id r0FBMRBq001875 for
 <receiving.mail@address.com>; Tue, 15 Jan 2013 12:22:27 +0100
Received: from webserver (Unknown_Domain []) by sending.mail.server.com
 (Corporate mail) with SMTP id 30.F9.03654.3FB35F05; Tue, 15 Jan 2013 12:22:27
 +0100 (CET)
Content-Class: urn:content-classes:message
Subject: The Subject
Date: Tue, 15 Jan 2013 13:22:26 +0200
Message-ID: <50.F9.03654.3FB35F05@sending.mail.server.com>
Thread-Topic: The Subject
Thread-Index: Ac3zEpv+A9o/QUbWTMmfmvqg/aBDEg==
From: Web Service <their@email.com>
To: "Name of user" <receiving.mail@address.com>
MIME-Version: 1.0

Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Is it common that e-mail messages gets rebuilt during transmit and what are the most common causes for this? How do you prevent this from happening?


Email are indeed modified as they traverse systems but the only thing that should be getting changed is the headers, where they add information about the system they are passing through. The body should never be modified.

  • Exactly what I thought too but the content must definitely been changed between the endpoints. Completely different MIME-boundaries although originating from the same server is proof enough (?). – m__ Jan 17 '13 at 9:37

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