Re-posted From Microsoft http://office.microsoft.com/en-us/outlook-help/overview-of-the-junk-e-mail-filter-HP010355048.aspx

Overview of the Junk E-mail Filter

The Microsoft Outlook 2010 Junk E-mail Filter helps to reduce unwanted e-mail messages in your Inbox. Junk e-mail, also known as spam, is moved by the filter away to the Junk E-mail folder.

How the Junk E-mail Filter works

The Junk E-mail Filter evaluates each incoming message to assess whether it might be spam, based on several factors. These can include the time when the message was sent and the content of the message. By default, the Junk E-mail Filter is turned on and the protection level is set to Low. This level catches only the most obvious spam. You can make the filter more aggressive by changing the level of protection that it provides.

 Note    The Outlook Junk E-mail Filter does not stop delivery of junk e-mail messages, but moved suspected spam to the Junk E-mail folder.

You can adjust the Junk E-mail Filter settings in the Junk E-mail Options dialog box.

• On the Home tab, in the Delete group, click Junk, and then click Junk E-mail Options.

Junk E-mail folder

Any message that is suspected to be junk is moved to the Junk E-mail folder. We recommend that you periodically review the messages in the Junk E-mail folder to check for legitimate messages that were incorrectly classified as junk. If you find a message that is not junk, drag them back to the Inbox or to any folder. You can also mark the item as not junk by doing the following:

• On the Home tab, in the Delete group, click Junk, and then click Not Junk.

Junk E-mail Filter Lists

While the Junk E-mail Filter checks your incoming messages automatically, the Junk E-mail Filter Lists give you more control over what is considered spam. You can add names, e-mail addresses and domains to these lists so the Filter allows messages from sources that you trust, or blocks messages that arrive from specific e-mail addresses and domains that you don't know or trust.

Safe Senders List     E-mail addresses and domain names in the Safe Senders List are never treated as junk e-mail, regardless of the content of the message. You can add your Contacts and other correspondents to this list. If you use an Exchange account, all names and addresses in the global address list (GAL) are automatically considered safe.

Safe Recipients List     If you belong to a mailing list or a distribution list, you can add the list sender to the Safe Recipients List. Messages sent to these e-mail addresses or domain names are never treated as junk, regardless of the content of the message.

Blocked Senders List     You can easily block messages from particular senders by adding their e-mail addresses or domain names to the Blocked Senders List. When you add a name or e-mail address to this list, Outlook moves any incoming message from that source to the Junk E-mail folder. Messages from people or domain names that appear in this list are always classified as junk, regardless of the content of the message.

Blocked Top-Level Domains List     To block unwanted e-mail messages that come from another country/region, you can add country/region codes to the Blocked Top-Level Domains List. For example, selecting the CA [Canada], US [United States], and MX [Mexico] check boxes in the list would block messages from e-mail addresses that end in .ca, .us, and .mx.

Blocked Encodings List     To block unwanted e-mail messages that appear in another character set or alphabet, you can add encodings to the Blocked Encodings List.

E-mail account types supported by the Junk E-mail Filter

The Junk E-mail Filter can be used with the following kinds of e-mail accounts:

• Exchange accounts in Cached Exchange Mode
• Exchange account that delivers to an Outlook Data File (.pst)
• POP3 account
• IMAP account
• Outlook Connector for Windows Live Hotmail
• Microsoft Outlook Connector for IBM Lotus Domino

If you want to change your profile, export a copy of the Junk E-mail Lists before you make the changes, and then import the information into Outlook. This ensures you will not have to re-create the Junk E-mail Filter Lists.

To Learn more about the function and use of Outlook 2010 Junk Mail Filtering, go to http://office.microsoft.com/en-us/outlook-help/overview-of-the-junk-e-mail-filter-HP010355048.aspx