E-Mail - E-Mail Services - Junk E-Mail Filtering - Advanced Options

This article describes our advanced junk e-mail filtering options. If you haven't already, please first read the Junk E-mail Filtering Overview.

If you've already enabled junk e-mail filtering and just need to set up your e-mail reader, please read Junk E-Mail Filtering And Your E-Mail Reader.

DNSBLs

A DNSBL, or DNS Blackhole List, is a service that maintains a list of sites believed to be responsible for large volumes of junk e-mail. You can choose to have your e-mail checked against DNSBLs for determining a SpamAssassin junk e-mail score. SpamAssassin uses a scoring system to determine which e-mail messages are junk and which are legitimate.

You can enable the DNSBLs that SpamAssassin uses for junk e-mail scoring by following the steps below:

1. Log into the Account Control Center (https://my.pair.com).
2. Click E-mail Management.
3. Click Junk E-Mail Filter Settings.
4. Click Junk E-Mail Filter Settings for Advanced Users.
5. Select the "Use SpamAssassin DNSBLs for junk e-mail filtering scoring."
6. Click Commit Changes.

Please do not enable this option unless you are completely familiar with DNSBLs and the implications of using this option. This option is not recommended for inexperienced users.

Spamhaus ZEN

pair Networks also grants you access to a DNSBL called Spamhaus ZEN (visit spamhaus.org for more information) to reject junk e-mail messages and to block those addresses that send junk e-mail.

You can enable Spamhaus ZEN by following the steps below:

1. Log into the Account Control Center (https://my.pair.com).
2. Click E-mail Management.
3. Click Junk E-Mail Filter Settings.
4. Click Junk E-Mail Filter Settings for Advanced Users.
5. Select the "Use Spamhaus ZEN to reject e-mail that Spamhaus flags as junk."
6. Click Commit Changes.

Please do not enable Spamhaus ZEN unless you are completely familar with DNSBLs.

Bayesian Filtering

A Bayesian Filter works by studying the words found in normal and junk e-mail. It uses this analysis to determine the probability that future e-mails are junk by looking at the words they contain.

Bayesian Filtering can also be enabled in the E-mail Management section of the Account Control Center on the "Junk E-Mail Filtering Settings for Advanced Users" page.

The filter will not begin to affect the scores of scanned e-mails until it has already learned from 200 junk e-mails and 200 regular e-mails. E-mails with especially high or low scores are learned automatically, but the process may take several weeks before the filter becomes active.

If you have files containing junk or regular e-mails you wish the filter to learn, you may connect via SSH and use the sa-learn command:

To learn a file of junk e-mail messages, use:

sa-learn --spam --mbox filename

To learn a file of regular e-mail messages, use:

 sa-learn --ham --mbox filename

For a complete list of options, run:

 sa-learn --help 

E-mail files being learned must be less than 30MB in size. Be sure to remove any e-mail that has already been learned before sending the file to sa-learn -- these e-mail messages will not be learned again but will still count toward the Bayesian Filtering limit.

The system transfers e-mail files to the e-mail filtering server for Bayesian Filtering learning every 20 minutes.

Qmail Junk E-Mail Filtering Option

This option allows you to apply any enabled junk e-mail filter feature such as greylisting, e-mail virus scanning, and SpamAssassin to your .qmail files. Final e-mail delivery is handled by Qmail regardless of the junk e-mail filtering options.

Customer Preferences File

In addition to the SpamAssassin preferences file created by your choices in the Account Control Center, you can keep a preference file in your home directory. This file should be named user_prefs and located in the directory /usr/home/username/.spamassassin/. The maximum size for your customer preferences file is 15k.

Useful uses for this file include:

• Setting a custom score for mail to be considered junk:

  required_score 9.5
  

• Disabling certain rules:

  score SOME_RULE 0
  

• Whitelisting/blacklisting addresses:

  whitelist_from janedoe@example.com
  blacklist_from junkmailer@example.net
  

  This is especially useful for uploading large lists or dynamically maintaining the list.

  NOTE: When working with the raw configuration file, * must be used as a wild-card character. For instance, use *@example.com to block all mail from example.com.

Additional Resources:

• Junk E-Mail Filtering Overview
• Junk E-Mail Filtering And Your E-Mail Reader
• SpamAssassin