ITS runs a Spam filter software called Amavisd at the mail gateway. This in turn feeds each mail message through anti-Spam software called SPAM ASSASSIN. Spam Assassin uses a number of mechanisms to give each message a score based on many attributes often found in Spam email. The messages are also checked against online databases on well-known spammers.
Effectively managing SPAM
Spam Assassin use a combination of methods to decide whether an email is likely to be spam. They can:-
- Block email that comes from addresses on a blacklist. This can be a commercially available list or a "local" list of addresses that have sent spam before.
- Check whether email comes from a genuine domain name or web address. Spammers often use fake addresses to try to avoid anti-spam programs.
- Look for keywords or phrases that occur in spam (e.g. "credit card", "lose weight")
- Look for patterns that suggest the email's sender is trying to disguise their words (e.g putting "hardc*re p0rn")
- Look for unnecessary HTML code (the code used for writing web pages) used in email, as spammers often use this to try to conceal their messages and confuse anti-spam programs.
- The emails which are guaranteed to be SPAM are deleted.
- Whilst emails which do not score enough points to be classed as fully SPAM are tagged as ***SPAM*** in the subject. These tagged message are then delivered to you for you to decide and delete if it is really a SPAM.
- You can use the mail filtering capabilities of your email program to manage these marked messages effectively. It is advisable when setting mail rules for spam mails to move them to a folder which you could name as Junk folder, rather than to the Deleted items folder since some genuine mails might also be marked as spam.
- Then you can review this folder later to pick out your genuine messages.
The difficulty for any Spam filter is to be able to distinguish good email from Spam accurately, without wrongly deleting any legitimate messages. In addition Spammers are constantly trying to find ways to disguise their messages and fool anti-spam software. In response to this challenge, ITS continually revises its strategies for detecting spam by keeping abreast with the latest updates and techniques available.
Click on the links below for instructions on setting SPAM mail filter in the following email programs:-