We can now preview the image file of the Dynamics 365 email.
https://docs.microsoft.com/en-us/dynamics365/customer-service/customer-service-hub-user-guide-email-overview#preview-image-attachments

Similarly, if the timeline note or email attachment are something other than an image, we want it to be previewed on the browser.

There are two reasons why we want this behavior.
-We want to save the time of downloading and opening some file locally.
-The file may contain sensitive information. We want to avoid having multiple users download and keep saving locally.