You may find it useful to create your own filtering rules, to augment or even replace your mail program's automatic filtering capabilities. For example, you might want to always trash email from anyone at xyz.com. Instead of having the Bayesian filter in, say, Eudora 6 do the filtering, you can make a rule manually that says, "If the From address contains 'xyz.com', transfer the message to the trash." When mail arrives from domain xyz.com, the manual rule executes, sending the message to the trash, so the Bayesian filter doesn't even see the message. For a simple filtering condition like this, it's somewhat more efficient to use a manual rule than the more complex Bayesian filter.

Manual filters are typically built by specifying a condition and an action. Conditions might be

• the From address contains certain text, like "xyz.com"
• the Subject line contains certain text, like "viagra"

and actions might be

• transfer the message to the Trash folder
• change the font of the message's subject line to red

In each of these three mail clients, the manual rules are executed before the automatic rules. The specifics of how to create rules manually are covered in each product's documentation.

• OS X's Mail - From the Mail menu choose Junk Mail, then Custom.
• Eudora 6 - From the Windows menu choose Filters.
• Mailsmith - From the Window menu choose Mail Filters.

For email programs without automatic rule-building, manually created rules are the only way to do filtering.

• Outlook Express - From the Tools menu choose Rules.
• Entourage - From the Tools menu choose Rules.
• Netscape - From the Tools menu choose Message Filters.
• PowerMail - From the Setup menu choose Mail Filters.
• QuickMail Pro - From the Tools menu choose Mail Manager.