This option protects only against mail from individuals and domains in your Blocked Senders list, moving it to the Junk E-Mail folder. All other mail is delivered to your Inbox.

This option functions essentially like the junk e-mail and adult content filters in earlier versions of Outlook 2007. Outlook 2007 uses a predefined filter to scan the body and subject of messages to identify likely spam.

You can’t specify additional filter criteria for subject or content checking for this junk e-mail filter, although you can create your own custom junk e-mail rules to block messages using additional criteria.

This level uses the same filtering as the Low level, but it also uses additional message scanning logic to determine whether a message is spam. Outlook 2007 scans the message body and message header for likely indications that the message is spam. You do not have any control over this scanning, other than to enable it by choosing the High scanning level.

If you choose the High option, you should not enable the option to delete junk e-mail messages rather than move them to the Junk E-Mail folder. Although Outlook 2007 will catch most spam, it will also generate false positives, blocking messages that you expect or want. You should review the Junk E-Mail folder periodically and mark any valid messages as not being junk e-mail. Marking messages in this way is explained in "Marking and Unmarking Junk E-Mail" later in this chapter.

This level provides the most extreme message blocking. Only messages originating with senders in your Safe Senders and Safe Recipients lists are treated as valid messages, and all others are treated as junk e-mail.

Although this protection level offers the most chance of blocking all of your junk mail, it also offers the most chance of blocking wanted messages. To use this level effectively, you should allow Outlook 2007 to place messages in the Junk E-Mail folder and review the folder periodically for valid messages. When you find a valid message, add the sender to your Safe Senders list.

Outlook 2007 maintains three lists: Safe Senders, Safe Recipients, and Blocked Senders. Figure 12-2 shows a Blocked Senders list, which blocks all messages from these senders. Messages originating from an address or a domain on the list are filtered out. Entering a domain in the Blocked Senders list blocks all messages from that domain, regardless of the sender. Add wingtiptoys.com to the list, for example, and Outlook 2007 would block messages from [email protected], [email protected], and all other e-mail addresses ending in @wingtiptoys.com.

Figure 12-2. Use the Blocked Senders list to block messages by address or domain.

The Safe Senders and Safe Recipients lists identify senders and domains that Outlook 2007 should not filter, regardless of subject or content. Use the Safe Senders list to identify valid messages by their originating address. Use the Safe Recipients list to identify valid messages by their target address. For example, if you participate in a mailing list, messages for that list are sometimes addressed to a mailing list address rather than your own address, such as [email protected] rather than [email protected]. Add the mailing list address to the Safe Recipients list to prevent Outlook 2007 from treating the mailing list messages as junk e-mail.

You have two options for adding entries to each of the three filter lists: specify an e-mail address, or specify a domain. As mentioned earlier, if you specify a domain, Outlook 2007 blocks all messages from that domain, regardless of sender. However, Outlook 2007 is rather selective in blocking. Specify @wingtiptoys.com, for example, and Outlook 2007 will block messages from [email protected] and [email protected] but will not block messages from [email protected]. You must specify the subdomain explicitly in a list to either accept or block that subdomain. For example, to block the subdomain sales.wingtiptoys.com, enter sales.wingtiptoys.com in the Blocked Senders list.

Outlook 2007 also lets you specify a set of top-level domains and language encodings to block as part of its junk e-mail filtering. These options are set on the International tab by selecting the desired domains and encodings from the provided lists.

Outlook 2007 by default moves junk e-mail to the Junk E-Mail folder, which it creates in your mailbox. The Junk E-Mail folder gives you the capability to review your junk e-mail messages before deleting them. If you prefer, you can configure Outlook 2007 to delete messages instead of placing them in the Junk E-Mail folder. As a general rule, you should configure Outlook 2007 to automatically delete messages only after you have spent a month using the Junk E-Mail folder, adding senders to your Safe Senders list and otherwise identifying to Outlook 2007 valid messages that have generated false positives.

Postmarks are a method of adding a "cost" to each e-mail message as a means of discouraging spammers. When you send a message, a unique postmark is generated using information from that specific piece of e-mail, such as recipients and the time that it was sent. This costs a certain amount of computational power and time, although not really enough for the typical Outlook 2007 user to notice. A spammer sending thousands of messages an hour, however, would definitely see a performance hit—in theory, enough to require additional computers for processing—and thus be discouraged from using postmarks.

When a mail client that supports Outlook 2007 e-mail postmarking receives a message, it includes the presence (or lack) of a postmark in its junk e-mail evaluation process. E-mail with a postmark is seen as much less likely to be spam.

Even when you have enabled this feature by selecting When Sending E-Mail, Postmark The Message To Help E-Mail Clients Distinguish Regular E-Mail From Junk E-Mail on the Options tab, not all outgoing messages are postmarked. For example: