Polymail - Native email app for email productivity.

Encrypto - Encrypto lets you encrypt files before sending them to friends or coworkers.

Airmail - Airmail is a lightweight and lightning fast mail client for Mac.

MagicPad - Free, simple, and private, offline text encryption suite.

Spark Mail - Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues

Tresorit - Encrypted cloud storage for your confidential files. Using Tresorit, files are encrypted before being uploaded to the cloud. Start encrypting files for free.