When creating a new email encryption can be found under options.

Outlook classic:

Outlook new: Once you send the encrypted email this is what the recipient will see. 

After clicking on Read the Message this is what you should see. They should click Sign in with a One-time passcode. 

They will then receive another email with a one time passcode.Once they receive this code they will enter it. After entering the code they will then be able to see the email.