Can We Fire Someone for What They Said in Personal Email?

An employer discovered that one of its employees left her outside email account open on her desktop.  The employer read some of her mail and saw that the employee sent a message to a friend stating that she hates her supervisor.  The employer wants to know if they have a legal leg to stand on if they fire the employee.  This article discusses employers’ rights and factors to consider before taking any action in this type of situation.