You can create custom Rule filters to make Spamfire accept or reject certain messages based on their contents. For example, you can create a rule that tells Spamfire to accept any message whose subject contains "Web order form" or reject any message that contains the word "viagra."
You can create and edit Rule filters in the Rule Filters Preferences Window.
Rule filters can check any portion of a message. Rule filters can include multiple criteria. For example, you could choose to accept messages if the subject contains the word "invoice" AND an attachment is named "invoice.doc".
Rule filters take priority over all other filters. Thus you can use Rule filters to override decisions made by other filters. One handy application of this is to create a rule filter to deal with spam from spoofed email addresses.
The results from Rule filters are used to automatically train the Bayesian filters. When you first start using Spamfire, the Bayesian filters will not be very good at identifying email. To avoid false positives, you could create a few Rule filters that accept any message that contains a keyword of interest to you. For example, if you receive customer orders emailed from your company Web site, you certainly don't want to miss them. You can create a Rule that accepts any message with "Web order" in the subject (or whatever). This will ensure that those messages are accepted. Even better, it will automatically train the Bayesian filters to recognize those messages as good. This can speed up your training time and reduce the number of corrections you have to make.
Rule filters are slightly different in version 2 than they were in version 1.6.