On a computer there are ways to truly protect saved files, and to protect E-mail from prying eyes. While there are lots of strategies, perhaps the easiest way to protect files and E-mail is to password protect and encrypt everything. Password protection can restrict access to protected files. Most word processing programs come with the ability to assign a password to a file, and using a password will typically also encrypt the file. Without the password no one can get access to the saved document.
Encryption means that the file is unreadable by any program without the encryption key or password.
In MS Word the sequence for password protection is File, Save As, Tools, General Options, Password, and in WordPerfect the sequence is File, Save As, and click the Password box on the menu. In both cases the file is encrypted. Password and encryption programs are available for lots of uses, and an Internet search will turn up thousands. A search for password recovery and decryption programs that break into files will also turn up quite a few. While the encryption that comes with most programs is getting better, it is still considered 'soft' encryption.