Information
This policy setting controls whether Outlook downloads untrusted pictures and external content located in HTML e-mail messages without users explicitly choosing to download them.
Note: If Outlook's default blocking configuration is overridden, in the Trust Center or by some other method, Outlook will display external content in all HTML e-mail messages, including any that include Web beacons.
The recommended state for this setting is: Enabled.
Rationale:
Malicious users can send HTML e-mail messages with embedded Web beacons, which are pictures and other content from external servers that can be used to track whether specific recipients open the 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.
Impact:
None - This is the default behavior.
Solution
To establish the recommended configuration via GP, set the following UI path to Enabled:
User Configuration\Administrative Templates\Microsoft Outlook 2016\Security\Automatic Picture Download Settings\Display pictures and external content in HTML e-mail
Default Value:
Enabled. (Outlook does not download external content unsafe content.)
Additional Information:
Note: By default, Outlook does not download external content in HTML e-mail and RSS items unless the content is considered safe. Content that Outlook can be configured to consider safe includes:
Content in e-mail messages from senders and to recipients defined in the Safe Senders and Safe Recipients lists.
Content from Web sites in Internet Explorer's Trusted Sites security zone.
Content in RSS items.
Content from SharePoint Discussion Boards.
Users can control what content is considered safe by changing the options in the Automatic Download section of the Trust Center. If Outlook's default blocking configuration is overridden, in the Trust Center or by some other method, Outlook will display external content in all HTML e-mail messages, including any that include Web beacons.