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Email Encryption for Windows


Outgoing Mail Filter

This page configures how SecExMail filters SMTP email headers to further protect your privacy.

smtpfilter





Every email message bears a unique fingerprint or message identifier which may be used to track the message across a network or indeed across the global internet. Further, each email reply contains a fingerprint correlator that allows the reply to be uniquely associated with the original message. SecExMail allows you to remove both message fingerprints as well as fingerprint correlators. Note that this will also disable message threading functionality in email client software.

Remove message fingerprint from cipher emails



Check this option if you want SecExMail to eliminate "Message-ID:" header information from encrypted emails. Modifying this setting will have immediate effect.

Shown below is an excerpt from a typical SMTP header containing a Message-ID fingerprint :


Return-Path: <yourname@offshoremailroom.com>

Delivered-To: john_doe@offshoremailroom.com

Received: from (HELO yourmachine_name) (yourname@203.134.3.41)

by localhost with SMTP; 23 Jul 2002 09:52:57 -0000

From: "Your Name" <yourname@offshoremailroom.com>

To: <john_doe@offshoremailroom.com>

Subject: Testing

Date: Tue, 23 Jul 2001 10:55:35 +0100

Message-ID: <000221c27717$gax278f1$0800a8c0@yourname>

MIME-Version: 1.0


The same header would appear as follows with the Remove message fingerprint option checked :


Return-Path: <yourname@offshoremailroom.com>

Delivered-To: john_doe@offshoremailroom.com

Received: from (HELO yourmachine_name) (yourname@203.134.3.41)

by localhost with SMTP; 23 Jul 2002 09:52:57 -0000

From: "Your Name" <yourname@offshoremailroom.com>

To: <john_doe@offshoremailroom.com>

Subject: Testing

Date: Tue, 23 Jul 2001 10:55:35 +0100

MIME-Version: 1.0



Remove fingerprint correlators from cipher emails



Check this option if you want SecExMail to eliminate "In-Reply-To:" header information from encrypted emails. Modifying this setting will have immediate effect.

Shown below is an excerpt from a typical SMTP header containing a fingerprint correlator :


Return-Path: <yourname@offshoremailroom.com>

Delivered-To: john_doe@offshoremailroom.com

Received: from (HELO yourmachine_name) (yourname@203.134.3.41)

by localhost with SMTP; 23 Jul 2002 09:52:57 -0000

From: "Your Name" <yourname@offshoremailroom.com>

To: <john_doe@offshoremailroom.com>

Subject: Testing

Date: Tue, 23 Jul 2001 10:55:35 +0100

Message-ID: <000221c27717$gax278f1$0800a8c0@yourname>

In-Reply-To: <000801c23789$3r040dc0$1441a8c0@nimitz>

MIME-Version: 1.0


The same header would appear as follows with the Remove fingerprint correlators option checked :


Return-Path: <yourname@offshoremailroom.com>

Delivered-To: john_doe@offshoremailroom.com

Received: from (HELO yourmachine_name) (yourname@203.134.3.41)

by localhost with SMTP; 23 Jul 2002 09:52:57 -0000

From: "Your Name" <yourname@offshoremailroom.com>

To: <john_doe@offshoremailroom.com>

Subject: Testing

Date: Tue, 23 Jul 2001 10:55:35 +0100

Message-ID: <000221c27717$gax278f1$0800a8c0@yourname>

MIME-Version: 1.0



Remove message fingerprint from plain emails



Check this option if you want SecExMail to eliminate "Message-ID:" header information from clear text emails. Modifying this setting will have immediate effect.

Remove fingerprint correlators from plain emails



Check this option if you want SecExMail to eliminate "In-Reply-To:" header information from clear text emails. Modifying this setting will have immediate effect.

Erase Computer Name from EHLO command



Email clients initiate the SMTP handshake with the EHLO command or "Hello" command. Usually the EHLO command will be used to identify your computer to the mail server. If you operate on a private network and behind a firewall the EHLO command will disclose your computer's true identity even if the firewall is used to mask your private IP address. This can be useful information to a hacker in locating sensitive information on a corporate network should firewall security ever be compromised. Check "Erase Computer Name" if you want SecExMail to erase your computer's identity from the EHLO command. Modifying this setting will have immediate effect.

Shown below is an excerpt from a typical SMTP header containing EHLO computer identity information :


Return-Path: <yourname@offshoremailroom.com>

Delivered-To: john_doe@offshoremailroom.com

Received: from (HELO yourmachine_name) (yourname@203.134.3.41)

by localhost with SMTP; 23 Jul 2002 09:52:57 -0000

Date: Tue, 23 Jul 2001 10:55:35 +0100


The same header would appear as follows with the Erase Computer Name option checked :


Return-Path: <yourname@offshoremailroom.com>

Delivered-To: john_doe@offshoremailroom.com

Received: from (HELO ) (yourname@203.134.3.41)

by localhost with SMTP; 23 Jul 2002 09:52:57 -0000

Date: Tue, 23 Jul 2001 10:55:35 +0100



The exact message layout depends on your mail server and email client software.
The SMTP protocol uses the HELO command. EHLO is used by the Extended Simple Mail Protocol ( ESMTP ).