The many different Microsoft Outlook versions have a way to block images linked to emails, that includes the so-called ‘spy pixels’ used by many companies.
You can choose to view pictures in an Outlook email by clicking a button at the top of each message.
Not sure which ‘Outlook’ you have? Check out The many faces of Microsoft Outlook.
Some Outlook’s block images by default, others don’t. It’s an ‘all or nothing’ feature which controls all images linked in an email, not just tiny ‘spy’ images.
Microsoft has been deaf to requests for a more subtle option which allows larger, visible, images but blocks tiny ones.
Outlook for Windows
Outlook for Windows has been able to block linked images for a long time. You’ve probably seen a message like this above emails.
Click on the message to let images download and appear in the message.
Trusted senders can be excluded from this automatic blocking.
All the controls for this feature are at Options | Trust Center | Automatic Download.
Outlook for Mac
It’s much the same on Outlook for Mac. A warning and choice above the message.
The control is at Preferences | Reading | Security. ‘Automatically download pictures from the Internet’ – all messages, contacts only or never.
Outlook Web App – browser
Outlook’s browser-based version has the same choice above the message.
How it looks depends on which version of ‘OWA’ you’re given, meaning which version of Exchange Server. Here’s a different look for the same thing.
Outlook Mobile Apps
For the Outlook Mobile apps (Apple or Android), the blocking option seem to be OFF by default. The other Outlook versions have blocking on from the start.
Go to Settings | Account Settings and turn on ‘Block External Images’.
Then the blocking option will appear above messages.