Encrypt emails with ProtonMail on your iPhone
Use ProtonMail when you need to send private information
For those occasions when you need to send personal and private information that only the intended recipient can read, use ProtonMail (protonmail.com). Accounts are free, and the app is free on the iPhone.
Email messages are sent through mail servers on the internet. Although communications between mail servers are secure, messages are decrypted on each server, which raises the possibility of them being read. ProtonMail encrypts emails from end to end so they are secure and cannot be read, even if intercepted. It is also a useful to have an alternative account as a backup to whatever you use in Apple Mail.