Why do email images load automatically?
Email images load automatically when they are included as remote URLs and the email client or browser allows them to display. This can improve rendering, but it can also contact a third-party server and trigger a tracking pixel.
Explanation
Many newsletters do not embed their images directly inside the email. They include links to files hosted on an external server. When the email is opened, the email client may request those files to display them. The same mechanism can be used for invisible tracking pixels, which measure an open or a display. To reduce this risk, a safer preview can block external resources by default and let the user choose whether to load them.
Concrete example
Example: a newsletter image hosted on a marketing domain can be requested as soon as the message is opened. If the image is 1x1 pixel or contains a tracking URL, it can be used to measure an open.
Common mistake
Do not confuse blocking images with deleting HTML. Blocking external resources prevents automatic loading, but the HTML code remains analyzable and can still be cleaned or copied.
Sources & methodology
This content follows Outilo's editorial guidelines.