What are some alternatives?
When comparing GPGTools and Symantec Desktop Email Encryption, you can also consider the following products
Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
Microsoft BitLocker - BitLocker is a full disk encryption feature included with Windows Vista and later.
GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
FileVault - FileVault is a method of using encryption with volumes on Mac computers.
GPG Suite - Use GPG Suite to encrypt, decrypt, sign and verify files or messages.
VeraCrypt - When you need to know that your information is secure, VeraCrypt offers an added layer of protection. Their encrypting process keeps your files and data safe from prying eyes.