Gpg4win is an email and file encryption package for most versions of Microsoft Windows, which uses GnuPG public-key cryptography for data encryption.

The Bat! is an email program for Windows that protects the correspondence and empowers the users to handle large amounts of emails quickly and efficiently.

GPGTools which lets you send and receive secure, OpenPGP encrypted and signed messages.

Seahorse is a GNOME application for managing encryption keys and passwords in the GnomeKeyring.

Evolution is the official personal information manager for GNOME.

MailMate is an IMAP email client for macOS featuring extensive keyboard control, Markdown integrated email composition, advanced search conditions.