57. Filter Junk Mail  BEFORE YOU BEGIN 54 Configure a New Mail Account 55 Find and Read Messages and Attachments
 SEE ALSO 58 Create a Mailbox
If there is a downside to email, it would have to be what is commonly known as spam , or junk mail. Anybody who has ever used email has been plagued with junk messagesunsolicited business propositions , pornographic advertisements, get-rich-quick schemes, and even viruses and Trojan Horses (malicious programs that sneak onto your computer via innocuous means, such as in an email attachment). Some people get so much junk mail that their real, legitimate email is lost in the shuffle. What's really infuriating is that there's usually no good way to defend against this kind of onslaught. Sure, you could set up a rule to delete messages from a certain sender or with a certain subject, but junk mail always comes from different sender addresses and has constantly changing subject lines and content. What's an email user to do? Fortunately, Apple's Mail application helps you fight back. Mail contains a heuristics-based junk-mail filtering system that learns with time what kinds of messages you consider to be "junk" and which ones you don't. When you turn on junk mail filtering, Mail can operate in either of two modes: It can delete messages it determines to be junk, moving them into a special Junk folder, or it can simply mark junk messages with a certain color , allowing you to review them later. This latter mode, Training mode, is what you can use while Mail is "learning" how to spot junk messages. When the Mail program has gotten good enough at recognizing junk mail, you can put it into Automatic mode, keeping junk mail out of your face for good. | 1. | Enable Junk Mail Filtering Open the Mail Preferences dialog box and click the Junk Mail icon in the toolbar at the top. If it is not already checked, select the Enable Junk Mail filtering check box. 57. Filter Junk Mail  | | 2. | Train Mail to Recognize Junk Messages
Mail begins in Training mode, in which it leaves junk messages in your In mailbox, but doesn't do anything but mark the messages with a certain color (light brown) and a special symbol in the Flags column. This way, you can check which messages it has identified as junk mail, and make sure that the program has made the right decision before deleting those messages yourself.
| | 3. | Correct a Misidentified Junk Message
While Mail is in Training mode, you need to help it correctly identify junk mail and ignore messages that it mistakenly flags as junk.
For a message that Mail incorrectly identifies as Junk Mail but that you actually want to receive, select or open the message and then click the Not Junk button, which appears both in the brown header area of the message and in Mail's toolbar. This action adds an entry into Mail's heuristics database, so that future messages that share the characteristics of this message will have a higher likelihood of being allowed through.
For an unwanted message that didn't get marked as junk mail, select or open the message, and then click the Junk button in the toolbar to tell Mail that this kind of message is something it should catch.
| | 4. | Allow Mail to Remove Junk Messages The Mail application should spend at least a couple of weeks in Training mode, learning to identify junk mail properly. Judge for yourself when you're ready to let Mail start automatically deleting junk messages on its own instead of just turning them brown for your review.  TIP After a couple of weeks in Training mode, Mail gives you an informative message that reminds you that it might be time to switch to Automatic mode. When you deem Mail to be ready to go into Automatic mode, open the Mail Preferences window and click the Junk Mail icon; select the Move it to the Junk mailbox (Automatic) radio button. From that point on, all messages that Mail determines to be junk are automatically moved into the Junk mailbox for that account. TIP You might still see unwanted messages in your Inbox, even when Mail is in Automatic mode; these are messages that Mail is still not identifying as junk messages. You can continue to train Mail to trap these messages by selecting them and using the Junk button, which now moves the messages to the Junk folder as well as adding their contents to Mail's heuristics database. Mail is designed to err on the side of cautionit will sooner leave a junk message in your Inbox than send a legitimate message to the Junk mailbox. Just the same, it's a good idea to open up your Junk mailbox occasionally and look for "false positives," messages that Mail has incorrectly identified as junk mail. Use the Not Junk button to reprimand Mail for these transgressions and, with time, they won't happen any more. | | 5. | Fine-Tune Junk Mail Filtering
Mail's junk filtering depends on several exception conditions, which you can control using the check boxes in the Junk Mail tab of the Mail Preferences window. Mail's default behavior is to ignore messages that come from addresses in your Address Book or Previous Recipients list, or if the address contains your full name (something that spammers seldom do, because usually all they have are lists of email addresses). Deselect these check boxes if you want Mail to be stricter with these kinds of messages.
| | 6. | Set Advanced Junk Mail Filtering Options
Select the Perform custom actions (Click Advancedx to configure) radio button and then click the Advanced button to gain access to even finer detail regarding how Mail deals with junk mail. In the sheet that appears, you can define an arbitrary number of criteria for what causes a message to be flagged as Junk. For instance, Message is junk mail means that Mail's heuristics database determines that the message is likely junk. Sender is not in my Address Book ensures that if the message is sent to you by someone you know (who is listed in your Address Book , as discussed in 95 Add a Person to Your Address Book ), Mail's filters will never trap the message.
Use the button next to any of these criteria to remove them from Mail's junk filtering scheme, or click + in any line to add a new criterion (which you can then specify using the extensively populated drop-down list). Finally, you can choose between whether all or any of the criteria have to be met for messages to be marked as Junk, using the drop-down menu at the top of the sheet; if you change the sense to any , Mail will mark far more messages as Junk than otherwise .
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