Our spam firewall examines all the characteristics of a message and uses a complex system of scores to determine whether a message is spam. When an email reaches the spam scoring filter, our spam firewall assigns scores to all the properties of the message.

For example, the spam firewall examines:

• A message's header and subject line for offending characters or words
• The percentage of HTML in the message
• Whether a message contains an 'unsubscribe' link

These properties (along with many others) help the spam firewall determine a message's spam score. Our spam rules and scores are kept up-to-date so we can quickly counteract the latest techniques used by spammers.