There are two main types of email in today's environment: standalone email software and Web-based email. The ability to read any electronic mail message requires an email client application.
A standalone client is a self-contained executable application. (The term client is used because email applications are based on the client/server architecture.) Electronic mail messages are routed from several clients to a central server. The server redirects the mail messages to an anticipated destination—another client. (A server is a machine or process dedicated to managing devices or network traffic.)