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SpamAssassin Best Practices

10/06/07


  
Permalink 04:10:07 pm, by Jet-Screamer Email , 881 words   English (US)
Categories: Website Hosting Tips

SpamAssassin Best Practices

Spam is a never ending battle and it hasn't been getting any easier lately. Two factors are driving the increase in spam these past six months; the increasing number of home computers with broadband connections and the change in tactics by spammers to image spam.

The ever increasing number of home computers with broadband connections are sought after by spammers to be compromised or "zombied". This means the home computer is remotely controlled by a hacker without the knowledge of the home computer owner and mass emailing software is installed and running in the background spewing out the spam on the broadband connection.

Since they're not paying for the bandwidth, the use of image spam does not decrease their profits. Image spam is an email which contains random text (to fool spam filters) in the subject and first paragraph of the email body, followed by an embedded image which actually contains the spam message, usually pump and dump stock scams. To detect image spam requires optical character recognition which is highly demanding of the processing power of a mail server and an inaccurate science.

Most web hosting includes a spam fighting feature. One of the widest used is SpamAssassin. The rest of this article will review SpamAssassin best practices and applies to adjusting SpamAssassin settings via the Plesk control panel:

After logging into your Plesk control panel, under Services, click the "Mail" icon. This will bring up a list of your email accounts. Click on the email address that you want to alter the spam detection settings of, and on the next page, under tools, click the "Spam Filter" link and you'll arrive on the Spam filter configuration page.

Follow up:

If "Enable spam filtering" is not checked, check it to turn on the spam filter. The next setting, "Use server-wide settings", allows you to simply use the default server spam filter settings and not have to bother with the rest of the settings on this page. The default server spam filter settings for your server are set by your hosting company.

Note: to test if your SpamAssassin filter is working, email your account with the following text:
XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X

To set your own spam filter settings you'll need to adjust the following:

  • Hits required for spam: Certain spam characteristics are assigned different values or weights and the culmination of these is the total spam score for an email. Examples of these are; 4.3 Mentions Generic Viagra and/or 0.1 HTML link text says "click here". A moderate number of hits setting is 6 but you can experiment with lower or higher settings.

  • What to do with spam mail: This tells the mail server to either mark the email as spam and deliver it to you with an explanation of what got it flagged as spam, and with the full original email attached or to delete it. Delete it means exactly that, it will be gone, completely. So it is a good idea NOT to set this to "Delete" unless you are confident your settings will not result in false positives. The most common practice is to set up a filter on your local email client such as Outlook to deliver messages with "*****SPAM*****" to a folder other than your inbox and look over it periodically to make sure there are no false positives. Once you are comfortable with your settings you should change this setting to "Delete".

  • Modify spam mail subject: This is added to the beginning of the mail subject. By default this is "*****SPAM*****" but you can change it to whatever you would like here.

  • Spam detection alert text: Leave blank to get the mail server default message which includes the listing of the email's spam score. To use a custom error message place it here.

  • Trusted languages & rusted locales: Letters written in the specified languages and with the defined character sets will not be marked as spam (most users will not need to adjust this).

Along the top you will also see the tabs White List, Black List, and Trusted Networks.

  • White List: The White List is where you enter email addresses or email patterns you want to NEVER be identified as spam. An email pattern means you can allow an entire domain using an asterisk as a wild card, for example to allow all mail from yahoo you would add "*@yahoo.com".

  • Black List: The Black List is where you enter email addresses or email patterns you want completely blocked. An email pattern means you can block an entire domain using an asterisk as a wild card, for example to block all mail from yahoo you would add "*@yahoo.com".

  • Trusted Networks: Most users will not need to utilize this.

USEFUL TIP: If you send out a mailing list to a large number of people, you should give your message content a spam test. By setting your "Hits required for spam" to 1, checking "Mark as spam and store in mailbox", and emailing your mailing list message to yourself you will see where, if at all, it contains any content which would get your message flagged as spam by your recipients' mail servers. Don't forget to set your "Hits required for spam" back to a less restrictive number after completing your content a spam test.


  
Jet-Screamer.com provides website hosting, website design, and website maintenance. Our website hosting plans can be reviewed here.

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