More Details

By now you'll know that Spam Gate is an anti-spam appliance.  A hardware device that sits on your network filtering out the spam before it gets to your email server.  But how does it work?

Spam Gate's power comes from the fact that it does much more than apply a single spam test to each incoming email.  In fact, even before the email itself is looked at, Spam Gate is working hard to establish that it's coming from a legitimate source.  Only when Spam Gate is satisfied on that score will it proceed to subject the email to a barrage of spam tests.

The list of tests below is not complete, but it gives you an idea of the process:

• Is the inbound connection coming from a properly configured SMTP server?
• Is the IP address of the inbound connection black listed?
• Is this IP address known to send spam?
• Does the sending server have a valid HELO identifier?
• Is the connection coming from a foreign country?
• Is that country on the blocked or suspect countries list?
• Is it coming from a black listed domain?
• Is the sender black listed?
• Is the sender white listed?
• Does the email contain a virus?
• Does the email contain a link to a black listed website?
• Does the email contain a suspicious expression?
• When statistically compared to known spam message and known clean messages, is this email more like spam or more like a clean message?

This last test is known as Bayesian Inference.  Spam Gate collects all inbound and outbound mail and divides it into ‘spam' and ‘not spam'. It then uses these two databases to create a statistical ‘picture' of what ‘spam' looks like and what ‘not spam' looks like.  By comparing inbound emails to these pictures, Spam Gate can assign each one a ‘spam probability value' which in conjunction with the other tests can be used to accurately identify spam.  The great advantage of this mechanism is that over time Spam Gate's ‘picture' of what spam looks like gets more and more accurate, increasing its ability to filter spam.  At the same time, its ‘picture' of what ‘not spam' looks like gets more accurate too - decreasing the chances of false positives.

By using multiple tests, and combining their results, Spam Gate is able to filter spam with 99% accuracy while having a very low rate of false positives.  There are few other anti spam measures out there that can claim this degree of accuracy, and none that we know of that are as cost effective.