MailStore - MailStore Home - A 100% free single-private-user desktop solution
VeraCrypt - VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux.
Mail Backup X - Your one stop mail backup and archiving tool for Mac.
Axcrypt - AxCrypt - Password Protect Files With Strong Encryption. AxCrypt is the leading open source file encryption software for Windows.
MailSteward - MailSteward : The Ultimate E-mail Manager for Mac OS X
Windows BitLocker - This topic provides a high-level overview of BitLocker, including a list of system requirements, practical applications, and deprecated features.