how do you password protect the contents of an email on a MAC using the Apple email app?

david nevins wrote:

how do you password protect the contents of an email on a MAC using the Apple email app?

As in the recipient must enter a passcode to view the contents? I don't believe that's possible.

However, if you're concerned about security - Sign or encrypt emails in Mail on Mac - Apple Support

You can set Mac to require a password when waking from sleep/screen saver. Not specific to the Mail app, but it should keep out unauthorized users.