The rules in Outlook 2002 and earlier can't perform the sophisticated filtering that server-based or dedicated client-side antispam software can, but Outlook 2003's Junk E-mail Filter can suppress a high percentage of the spam that creeps through corporate defenses to penetrate your Inbox. Thus, you can view Outlook 2003's Junk E-mail Filter as another layer of defense against spam, much like you run a desktop antivirus tool to supplement the antivirus software you run on your servers. Outlook 2003's Junk E-mail Filter is one of many client-side antispam tools. For information about finding others, see the sidebar "Other Outlook Antispam Tools."
How the Junk E-mail Filter Works
If you opt for some level of junk email protection, Outlook 2003 begins to process new messages waiting in your Inbox as soon as it starts up and checks incoming messages as they arrive. If you don't want Outlook to look for junk mail, select Options from the Tools menu, click Junk E-mail, go to the Options tab, which Figure 1 shows, and select the No Automatic Filtering option. The default protection level is Low, meaning that Outlook will detect only obvious spam. Some users will prefer to start cautiously and leave the protection level set to Low. I set the protection level to High so that Outlook aggressively checks for spam and moves any message that seems to be spam into the Junk E-mail folder. Outlook automatically creates the Junk E-mail folder if it doesn't already exist, and you don't have the option to select another folder. The Options tab also lets you permanently delete junk mail immediately (the equivalent of using Shift+Delete to remove messages without putting them in the Deleted Items folder). I don't recommend this option unless you have a high degree of confidence in Outlook's spam filters, which you can gain by setting the filter to High and periodically checking your Junk E-mail folder to make sure Outlook isn't filtering out messages that you need to receive. The results I got from the High setting were so good that I now have Outlook permanently delete any spam that it detects.
You can't change the algorithm that Outlook 2003 uses to decide whether a message is spam, but you can help Outlook improve its level of accuracy by creating lists of safe senders and blocked senders. Safe senders are email addresses that you recognize and that you don't want Outlook to mark as spam senders. Blocked senders are the opposite—addresses or domains that you gather from spam messages that elude Outlook's filters. To block a sender, right-click a message and select Junk E-mail, Add Sender to Blocked Senders List. Outlook will add the sender's email address to its list of known spammers. You can add to the list anyone who doesn't appear in your Global Address List (GAL—to block messages from someone on your GAL, you can use a regular Outlook rule).
Outlook's Junk E-mail Filter performs the following actions:
- Checks email message addresses against your contacts, and assumes that any message from a contact is safe to deliver
- Checks email message addresses against the corporate GAL, and assumes that you want messages from anyone in the GAL
- Checks email message addresses against your Safe Senders List, and assumes that you want messages from anyone on this list
- Checks email message addresses against your Safe Recipients List (I explain this list below), and passes through any messages with matching addresses
- Checks email message addresses against your Blocked Senders List, and transfers any messages with matching addresses to the Junk E-mail folder
- Runs the spam filter to analyze messages' content. The filter generates a ranking (think of the ranking as being a number from 1 to 100) to determine whether a message seems, behaves, and feels like spam. The higher the number, the more Outlook believes the message to be spam. After determining the ranking, Outlook decides whether to put the message into the Junk E-mail folder. If you set a Low protection level, Outlook will route messages with relatively high rankings to your Inbox. If you set a High protection level, Outlook will route messages that even smell of spam to the Junk E-mail folder.
As I mentioned earlier, you should check the messages in your Junk E-mail folder from time to time before deleting them, just in case. You might find that your selected protection level is too aggressive and that Outlook is filing legitimate messages in the Junk E-mail folder. If Outlook consistently filters out messages from a specific correspondent, you can add that sender to your Safe Senders List to take care of the problem.
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