Messages in HTML format often include pictures or sounds. Sometimes these pictures or sounds are not included in the message itself but are instead downloaded from a Web server when the e-mail message is opened or previewed. This is typically done by legitimate senders to avoid sending extra-large messages. However, junk e-mail senders have used this capability to their advantage by including something called a "Web beacon" in these messages. A Web beacon notifies the Web server when you read or preview the message, validating the e-mail address and often resulting in more junk messages being sent to you.
To help protect your privacy and combat Web beacons, Microsoft Office Outlook 2003 is configured by default to not automatically download pictures and other content from the Internet when you display a message in Outlook. If an e-mail message tries to connect unannounced to a Web server on the Internet, Outlook blocks that connection until you decide to view the content. However, e-mail messages from or to e-mail addresses or domain names on the Safe Senders (Safe Senders List: A list of domain names and e-mail addresses that you want to receive messages from. E-mail addresses in Contacts and in the Global Address Book are included in this list by default.) and Safe Recipients (Safe Recipients List: A list of mailing lists or other subscription domain names and e-mail addresses that you belong to and want to receive messages from. Messages sent to these addresses will not be treated as junk e-mail.) Lists are treated as exceptions and the blocked content will be downloaded. This feature can also help you to avoid viewing potentially offensive material (for external content linked to the message), and, if you are on a low-bandwidth connection, to decide whether an image warrants the time and bandwidth to download it.
When Outlook blocks automatic picture downloads, areas in the message that should have a picture will appear as a red X placeholder instead, along with text explaining that Outlook has prevented automatic download of the image. When you place your cursor over the blocked image, the alternative text (alternative text: Used by Web browsers to display text during image downloads for users who have graphics turned off and for users who rely on screen-reading software to convert graphics on the screen to spoken words.) for the image explains that automatic download was prevented. The InfoBar (InfoBar: Banner near the top of an open e-mail message, appointment, contact, or task. Tells you if a message has been replied to or forwarded, along with the online status of a contact who is using Instant Messaging, and so on.) of the message also tells you that content has been blocked.
In the case of legitimate messages you receive, for example, a newsletter that you have subscribed to, you can download pictures and other content on a per-message basis by clicking the InfoBar or by right-clicking a blocked image. To make sure that content is automatically downloaded whenever you receive the newsletter, right-click the blocked image and select an option on the shortcut menu to update your Safe Senders or Safe Recipients List to include the e-mail address or domain that the newsletter was sent from or to. You can change settings about automatic picture download for all HTML messages that you receive by selecting options on the Security tab on the Options menu or by selecting an option on the shortcut menu of a blocked image.
Another way to see pictures that have been blocked by this feature is to click View in Internet Zone on the View menu of the open message. This downloads any content that Outlook blocked. Before you unblock the image, be sure the message is from someone you trust or is a message that you are expecting. When you open a message in the Internet zone, all content is displayed and any scripts in the message will run, including any malicious scripts the message might include that can damage files or propagate viruses. If you subsequently open the message without viewing it in the Internet zone, the content that was blocked by Outlook will continue to be blocked.
Outlook normally does not download pictures or other content from external servers except if the content is on a Web site in the Trusted sites zone. Your e-mail administrator can change this behavior so that content from any of the zones (Trusted sites, Local intranet, and Internet) will have content downloaded automatically or blocked automatically.
When you edit, forward, or reply to a message that references external content, your computer will again try to download the content. By default, Outlook is configured to display a warning message. If you proceed, the blocked content will be downloaded and included in the reply or forwarded message. You can turn off these warnings but this is not recommended.
When you print a message with content that has not been downloaded automatically, the blocked content is downloaded and will appear in the printed message.