A lot of companies read emails sent by their employees. If you are also worried that someone in your office may be secretly reading your email messages, here's something you can do to at least prevent the email snoopers at work from visiting links (URLs) that you share in your emails - use a password.
HideLinks is an online service that helps you password protect any web URL easily. You type in the URL and a password - HideLinks will then generate a new wrapper URL that you can pass in the email message.
The email recipients (or the snooper) will have to type the same password in order to visit the actual website.
Just make sure you don't put the password in the same email message as that will defeat the whole purpose.