Legitimate images that should reach the intended recipient are incorrectly detected and blocked by Image Control heuristics in Symantec Email Security.cloud. This results in a false positive.
Consider changing the sensitivity of the Heuristics filter to a lower setting. Log in to the Symantec.cloud console, and navigate to Services > Email Services > Image Control.
Note: It is not possible to adjust the heuristics themselves, only the sensitivity level.
If you do not obtain the desired results and cannot make further adjustments to the sensitivity level, use the following lists:
If you no longer have the image to add to the Approved Images list, consider setting the heuristics detection action to one of the following:
You can also use the mechanics available in other filters of the Symantec.cloud service, such as Anti-Spam and Data Protection.