Access the Mail application from the Start screen or from the search result. If you are in Desktop mode, just press the Win key to switch to the Start screen.
When the Mail program is loaded, press Win key + I to open the specific Settings page for this application. From there, choose the Accounts option.
After that, you will be presented with a list of all current accounts inside the application. Just choose the account in which you no longer want images to be automatically downloaded and displayed.
When you have accessed the email setting page, find the Automatically download external images option, and change it from on to off.
Exit the Settings page.