Mu4e - Starting with version 0.9.8, mu provides an emacs-based e-mail client which uses mu as its back-end: mu4e.
MailMate - MailMate is an alternative email client that was designed for the macOS.
aerc - Highly efficient and extensible email client for the terminal
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
Meli - Learn about any monument, anywhere,anytime in a single touch