A security feature to protect your confidential email messages from being intercepted and read by third parties. When an email message (or attachment) is encrypted, its contents are essentially scrambled during transit, and can only be descrambled by the end recipient. Almost all email encryption programs use a public key encryption standard known as open PGP, which when operated properly, is uncrackable.

Email encryption tools are generally simple, web-based services similar to Hotmail or Yahoo Mail, (incidentally, neither of which uses encryption), or else come as plug-ins to most existing email programs. Many email encryption services offer fee versions of their software for private, single-consumer use.