Email encryption?

Short answer is no. Its not a simple setting.

Long answer is yes, and PGP is what you are looking for. This isn't step by step instructions how to use PGP but you can find those on the link to GnuPG.

Protecting Security Information - Apple Support

S/Mime support is built-in to Apple Mail app

<How to Set Up Signed and Encrypted Email – Podfeet Podcasts>

<Use S/MIME to send encrypted messages in an Exchange environment in iOS - Apple Support>

Read the article : Mail for Mac: Sign or encrypt messages for increased security