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Spam glossary: explanations and notes on terms

• Spam
  Unsolicited bulk e-mails are known as spam or junkmail. Sending spam is illegal in some countries and is forbidden by the conditions of use of all responsible e-mail service providers, including the University of St Andrews.


• MailScanner
  This is the name of the software used for checking e-mail traffic for viruses and spam. It makes use of additional software:
  
  • Sophos anti-virus checks for viruses, using virus signature databases that are updated regularly
  • SpamAssassin checks for spam using a wide range of tests. There is no single test for spam, and SpamAssassin awards a score which indicates how likely the message is to be spam.


• Flagged messages
  When MailScanner identifies a message as a virus or as spam it places a flag in the Subject line of the message, either {Virus?} or {Spam?}.
  


• False positive
  Occasionally a genuine message is flagged as spam erroneously. These cases are known as false positives.


• Spam score
  In addition to the {Spam?} flag, SpamAssassin places additonal headers in the message, including one giving the spam score. The higher the spam score the more likely the message is to be spam.

Further notes on spam scores.

• Spam threshold
  Recognition of spam is never absolutely certain. One has to balance between the risk of false positives (genuine messages erroneously flagged as spam) and the risk of letting spam through unflagged. LIS has discovered that when a message has a spam score of 5 there is only a small chance of it being a genuine message. LIS therefore uses 5 as the threshold at which it treats a message as spam, and flags it. If the threshold were lowered, there would be more false positives; if it were raised there might be fewer false positives, but also more spam messages would get through unflagged. We don't recommend lowering the threshold.


• Filters
  If you want to prevent messages flagged as spam from getting into your In box you can set up a filter. You can create the filter
  
  • either within your client program
  • or on the server to discard messages that are flagged as spam before they are downloaded into your email client
  If you create a filter which discards messages that are flagged as spam you must be aware of the risk of false positives.