Follow the appropriate instructions below depending upon whether you are using the Outlook desktop program for Windows or using the Outlook web app in a browser like Chrom, Edge, or Firefox.  In order for these options to appear, you must have a Microsoft Exchange email account that supports encryption. 

Microsoft Outlook for Windows

Create a new message. 

Click "Options" at the top of the message and then click the Encrypt toolbar icon.

Microsoft Outlook Web Application

Create a new message. On the message toolbar, click "More Options" (three dots), then click Encrypt, and then click Encrypt just to the right of the first Encrypt.