Safe Recipients
The reasons for the Blocked Senders List and Safe Senders List are apparent; the purpose of the Safe Recipients List is less so. Essentially, a safe recipient is a distribution list (DL) or newsgroup from which you want to receive messages. You don't control the membership of the DL or newsgroup, but you assume that the administrator won't send spam to the members. You tell Outlook that you want the messages from the email address of the DL or newsgroup by designating the address as a safe recipient.
Building and Sharing Lists
After a while, you'll accumulate a list of blocked senders that you might want to share with others. You might also want to share lists of safe recipients or safe senders. You can export data from or import data into any list. Go to the Blocked Senders tab of the Junk E-mail Options dialog box, and click Export to File to generate a simple text file that you can manipulate with any text editor. You can append lists gathered from other users and share updated lists of known spammers in a central location so that anyone can import them into Outlook.
Note that you can also add complete domains to your Blocked Senders List to block any attempt to send you email from those domains. However, be careful not to be too enthusiastic about adding individuals or domains to the Blocked Senders List because long lists will slow down processing.
Performance
Even the best implementation of multilayer network protection against incoming spam will let some messages through. If you take the time to add the senders of any spam messages that get past the Junk E-mail Filter to the Blocked Senders List, Outlook's ability to recognize and block new spam will gradually improve. In my case, the Junk E-mail Filter intercepts most of the offending messages that make it past my company's bastion host and server-based spam filters, so very few spam messages actually reach my Inbox now.
In Outlook 2002 and earlier versions, rules can slow down message delivery, especially when they call for complicated processing such as the type necessary to detect spam. Outlook 2003 caches the lists it uses and implements the Junk E-mail Filter in compiled code, so performance is acceptable—I don't notice any delays with approximately 40 entries in my Blocked Senders List. Outlook 2003 doesn't perform junk mail filtering until it has fully downloaded the header and content of new messages, so if you're quick, you might see a message appear in the Inbox, then disappear after Outlook checks its content, decides that it's spam, and moves it into the Junk E-mail folder. Apart from that evidence, you shouldn't be aware that spam processing is going on.
The Exchange 2003 Connection
Outlook 2003 leverages some Exchange 2003 features. The client software stores the Safe Senders List and Blocked Senders List as well as its Junk E-mail Filter settings as properties of user mailboxes so that Outlook Web Access (OWA) 2003 can use the same data when it checks for spam. Figure 2 shows the Blocked Senders List for a mailbox as viewed through OWA 2003.
Antispam tools that run on Exchange 2003 servers can also exploit information about blocked senders, and Exchange honors the Blocked Senders List to direct email messages from those addresses into the Junk E-mail folder as soon as the messages arrive on the server (before Outlook ever gets involved). This feature means that clients don't need to incur the network and processing overhead to download and check the messages.
In addition, OWA 2003, like Outlook 2003, blocks external content to prevent spammers from confirming that email addresses to which they've sent messages are valid. The content might be a Web beacon, a small and often invisible graphic file that signals a spammer that a message has reached a real email address when a client downloads the file for display. (For more information about Web beacons, see "Spam Beacons," September 2003, http://www.winnetmag.com, InstantDoc ID 39501.) The golden rule here is to always avoid downloading anything when you're unsure of its source. Outlook 2003 and OWA 2003 will display the graphic content in messages from senders on your Safe Senders List. For example, I added Amazon.com to my Safe Senders List so that I could see details in order confirmations after I've bought something, and I added Unitedcomics.com so that I could see the Daily Dilbert cartoon that the company sends by email.
Outlook won't suppress all the spam that arrives at your organization, so be prepared to deploy bastion hosts and server antispam software to stop as much spam as you can before it gets anywhere near your clients. But every weapon that comes along to fight spam is welcome, so I'm glad to have client-side blocking incorporated into Outlook 2003.
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