Doman Name Server Block Lists (DNSBLs)

Introduction

DNSBLs are servers that hold continually updated repositories of known spammers. The IP addresses in downloaded emails are matched against the lists to determine if an email is spam or not.

SpamSquash uses two block lists "Spamhaus.org" and "Sorbs.net". You activate either one or both. When both are activated almost 80% of spam should be caught.

Advantage of DNSBL over Bayesian

The advantage of the DNSBL over Bayesian, is that the DNSBL can simply be turned on or off. The Bayesian requires training. The disadvantage, is that it doesn't achieve nearly the accuracy level of a Bayesian filter.

To learn more about them visit http://www.spamhaus.org/ and http://www.sorbs.net".

Using DNSBLs with the Bayesian Filter

This filter can be used in tandem with the Bayesian filter. When working together, you should be able to more effectively filter spam.

Use with White List

The DNSBL should be used with the white list. If you are on any email lists, or have any regular emailers from whom you want to receive email, then the white list should be used. DNSBLs do give false positives, and this will greatly reduce that problem. The number of false positive should be low, however.

The Filter's Accuracy

When both DNSBLs are on, the accuracy of the filter should be close to %80. That is, it will get about %80 of spam.

Activating the Filter

The first thing you need is your DNS IP address. To do this, see "Setting up DNS for DNSBLs", then come back here to read the rest.

Once you have the DNS working, to activate the filters go to the "DNSBL Filter Panel". To do this select he menu option "Filter/DNSBL Filter Panel", or press the "F" toolbar icon. Once the panel is up, you can turn a filter on or off, using the two drop down lists. When "Spamhaus.org" is selected, it becomes active. When "Sorb.net" is selected, it becomes active. You can use both, one, or neither. You should note in the status bar of SpamSquash the text "DNSBL ON", when the DNSBL is on.

Testing an Email Against the DNSBLs

You can determine if a specific email will be filtered by the activated DNSBL(s) by selecting the email in one of the folders, then by selecting the menu item "Filtering/DNSBL Test Email". If it's black listed, it will pop a window up with "Black Listed IP". If it's not black listed, it will come back with "Not on Black List".