SPAM FILTERING
 Unsolicited Commercial Email (UCE, also called SPAM) is big problem in today's corporate and ISP email systems. It's time to fight the SPAM with our Mail Server. We use multiple strategies for reducing the amount of SPAM that you and your users will have to put up with.
We have built three different strategies into the Mail Server to help you avoid the lost time and wasted resources of SPAM:
- Filtering Common SPAM Activities
- Email Content Filtering
- SpamAssassin™ Software
Filter Common SPAM Activity
Spammers often use predictable and detectable techniques when sending SPAM. Your Mail Server has been designed to can recognize these techniques and reject the message. Some of the techniques we use include:
- DNS check for valid mail server (MX record) of domain in senders address. This means if the email address of the sender does not have a valid mail server in the DNS system then it will be refused.
- Limits number of envelope recipients (RCP TO's) for incoming email to 50. Spammers often include hundreds of recipients on one email. Our Mail Server also uses a technique called "tar pitting", which causes a processing delay when a sender has excessive recipients; this is done deliberately to tie up the Spammer's resources
- Any email including a "%" sign in the SENDER and/or RECIPIENT address will be rejected.
- Email addresses containing the local host name, IP address, or reverse host name are rejected.
Email Content Filtering
We also filter through email content for known SPAM and virus patterns. Some of the basic filtering includes:
- Attachment Filtering: Because of the high risk of viruses and other problems, we automatically return all email with any of the following attachment types: .vbs, .lnk, .scr, .wsh, .hta, .pif.
- Content Filtering: There are certain keywords that when found in an email will cause the email to be returned to the sender. These include any email where the following keywords are found in the subject of the email: viagra, ADV:, XXX, EXPLICIT, TEENS, A D U L T S, ADLT:. This filtering is in addition to the Anti-SPAM Filtering described elsewhere.
SpamAssassin™
SpamAssassin™ is the leading anti-SPAM technology available on the Internet today. And is bundled with your Mail Server. SpamAssassin™ works by attempting to identify SPAM using text analysis. Using its rule base, it uses a wide range of heuristic tests on mail headers and body text to identify SPAM. SpamAssassin™ typically differentiates successfully between SPAM and non-SPAM in approximately 95-99% of cases, depending on the kind of mail you receive.
SpamAssassin™ uses the following strategies:
- Header Analysis: Spammers use a number of tricks to mask their identities, fool you into thinking they've sent a valid mail, or fool you into thinking you must have subscribed at some stage. SpamAssassin™ tries to spot these.
- Text Analysis: Again, SPAM mails often have a characteristic style (to put it politely), and some characteristic disclaimers and CYA text. SpamAssassin™ can spot these, too.
- Profile Matching: SpamAssassin™ uses a wide variety of local and network tests to identify SPAM signatures. This makes it harder for spammers to identify any one strategy that will allow their messages to get through.
- Scoring and Tagging: SpamAssassin™ works by scoring a message based on its content and headers. Matching on specific SPAM characteristics will raise the score of a message. Some characteristics even lower the score. After calculating the final score of the message, if the score is greater than 5.0, the message is tagged as SPAM so that it can be filtered by the user later using their regular email program.
Summary
We can't guarantee you won't get any more SPAM. But we can assure you that we have built a system that uses some of the best techniques and tools available any where to give you a state-of-the-art system for fighting back. |
