Often, end users use software or a graphical user interface (GUI) to write, send and receive emails., Also known as email clients, for example, Mozilla Thunderbird, Microsoft Outlook, etc., are customers of e-mail. The same tasks can be done through a web interface, that is, a web mail client interface. Some common examples of these are: Gmail, Yahoo mail and Hotmail
The mail you send from your client's interface travels through a series of specialized email servers that internally run software called the Mail Transfer Agent (MTA), and their main job is to route the email to destinations appropriate by analyzing the mail header.
Subsequently, the mail arrives at the recipient's mail server, which can be retrieved using his email client.
In this section we will review the main communication protocols that are used to send and receive emails...