Outlook 2016, 2013 and 2010 has a feature that allows users to always display email in plain text. If you want to increase the email security and avoid falling prey to scam emails with fraudulent website links then it advisable to turn on this feature.
Step 1: Click the File menu and select Options from the list.
Step 2: In the Outlook Options window, navigate to Trust Center tab.
Step 3: Click the Trust Center Settings button under Microsoft Outlook Trust Center section.
Step 4: Then Click the E-mail Security tab under Trust Center and mark the check box with caption as Read all standard mail in plain text.
This would display all the standard email in plain text format.