Protonmail is the answer to secure email. There are free accounts and paid accounts depending on what you are looking for.
There is also Tutanota, I haven’t used it yet but plan to to compare it to Protonmail. Tutanota is free.
ProtonMail also has their ProtonBridge, which connects to the ProtonMail application & servers, and encrypts & decrypts your Email from those servers for an IMAP or POP Email client application, like Thunderbird or Oulook. It is Free for all levels of paid ProtonMail subscribers.