Information
This policy setting controls whether pictures from sites in the Trusted Sites security zone are automatically downloaded in Outlook e-mail messages and other items.
The recommended state for this setting is: Enabled
Malicious senders can send HTML e-mail messages with embedded Web beacons, or pictures and other content from external servers that can be used to track whether specific recipients have opened a message. Viewing an e-mail message that contains a Web beacon provides confirmation that the recipient's e-mail address is valid, which leaves the recipient vulnerable to additional spam and harmful e-mail.
If a malicious sender is accidentally added to a user's Safe Senders List or Safe Recipients List, Outlook will display external content in all e-mail messages from the malicious sender, which could include Web beacons.
Solution
To establish the recommended state via configuration profiles, set the following Settings Catalog path to Enabled :
Microsoft Outlook 2016\Security\Automatic Picture Download Settings\Block Trusted Zones
Impact:
Outlook will not automatically download external content for messages sent by people listed in user's Safe Senders Lists or Safe Recipients Lists. This will cause users to have to download content for each message individually.