Anti-Spam uses advanced filtering rules to prevent unsolicited email messages from entering your Inbox. You can fine-tune which messages Anti-Spam identifies as spam by creating a custom filter.
For example, you can create a filter that searches your email for a specific word, like "mortgage." Anti-Spam marks any email with this word as SPAM and moves it to the Anti-Spam folder.
After you create a filter, check your Inbox to see how effectively it detects spam. If you find that many spam messages are delivered to your Inbox, you can edit the filter. For example, if you create a filter to look for a word in the subject of the message, but you still receive messages with that word, change the filter to look in the message body. Or keep the original filter, and add another filter to look in the message body.
 | Be careful not to create filters for common words that appear in legitimate email messages, because even legitimate email will be filtered. |
Advanced users can include regular expressions (regex) in custom filters. Regular expressions are special characters and sequences. To learn about regular expressions and how to use them, look on the web. For example, go to http://en.wikipedia.org/wiki/Regular_expression.