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Support - HOWTOs - Filtering Spam

As part of DNS Park's commitment to its customers, filtering Spam is a high priority. Second only to DNS services, providing quality email forwarding services is important to the Park.

In addition to blocking most Spam directly on our mail servers, we also analyze mail as it flows through our system. Using SpamAssassin we tag all of the email messages before they are delivered to you. Most email software clients have the ability to filter messages based on certain criteria. Using the anti-spam tags in the email headers, any Spam that we can't or don't stop at our mail servers can be sorted as you receive it.

This How-To will explain what information email should be filtered on to best prevent Spam. The process should be fairly straight forward, though we will not delve into configuring all the various mail clients available.

Below you will find an example of what is placed in the email headers when our Spam analysis takes place. The example is from a real piece of Spam that was received. The messages in the header of the message are generally not seen while reading email with most email clients so this information will silently be passed on unless it is explicitly looked at.

Date: Thu, 25 Jul 2002 16:18:35 -1900
MIME-Version: 1.0
Content-Type: text/html;
        charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
X-Spam-Status: Yes, hits=18.8 required=5.0
        tests=INVALID_DATE_TZ_ABSURD,NO_REAL_NAME,FROM_ENDS_IN_NUMS,
              PORN_14,CLICK_BELOW,EXCUSE_3,THIS_AINT_Spam,EXCUSE_13,
              HTTP_USERNAME_USED,PORN_4,BIG_FONT,CLICK_HERE_LINK,
              SLIGHTLY_UNSAFE_JAVASCRIPT,FREQ_Spam_PHRASE,PORN_3,
              FROM_AND_TO_SAME,CTYPE_JUST_HTML,DATE_IN_PAST_03_06
        version=2.31
X-Spam-Flag: YES
X-Spam-Level: ******************
X-Spam-Checker-Version: SpamAssassin 2.31 (devel $Id: SpamAssassin.pm,v
1.94.2.2 2002/06/20 17:20:29 hughescr Exp $)
X-Spam-Report:   18.8 hits, 5 required;
  *  4.4 -- Invalid Date: header (timezone does not exist)
  *  0.5 -- From: does not include a real name
  *  0.4 -- From: ends in numbers
  *  0.2 -- BODY: Uses words and phrases which indicate porn (14)
  *  1.5 -- BODY: Asks you to click below
  *  1.1 -- BODY: Claims you can be removed from the list
  *  0.9 -- BODY: Claims "This is not spam"
  *  0.1 -- BODY: Gives an excuse for why message was sent
  *  1.5 -- URI: Uses a username in a URL
  *  1.4 -- URI: Uses words and phrases which indicate porn (4)
  *  2.1 -- BODY: FONT Size +2 and up or 3 and up
  *  0.8 -- BODY: Tells you to click on a URL
  *  0.7 -- BODY: JavaScript code which can easily be executed
  *  2.4 -- Contains phrases frequently found in spam
            [score:  18, hits: click here, from our, our]
            [list, removed from, this email, this not, your]
            [email]
  *  0.5 -- Uses words and phrases which indicate porn (3)
  * -2.1 -- From and To the same address
  *  1.7 -- HTML-only mail, with no text version
  *  0.7 -- Date: is 3 to 6 hours before Received: date
X-Sanitizer: DNS Park mail filtering.
X-Sanitizer: For more information see http://www.dnspark.com/antiSpam.html

Based on the example, you will find a line that reads:

X-Spam-Flag: YES
Using your mail client, setup a filter that checks for this line and that message can be moved to another folder or deleted.
NOTE: We recommend that you do not immediately start deleting messages until you are comfortable with the filters in place so you don't accidentally delete something that is not Spam.