Email Introduction

E-mail is the most widely used application on the Internet.
A message consists of a header and a body. The format for headers is defined in RFC 5322.

Key Header Fields:

• From: The sender's email address.
• To: The recipient(s)'s email address(es).
• Subject: The subject line.
• Date: The date the message was sent.
• Cc (Carbon Copy): Additional recipients who receive a copy of the message but are not listed in the "To" field.

Mail Protocols

The mail system involves several protocols, including:

• SMTP (Simple Mail Transfer Protocol): Defines how information is exchanged between two communicating SMTP processes to transfer messages across networks.
• POP3 (Post Office Protocol version 3): A protocol used for retrieving and downloading emails from a server to a local client; it typically stores the message locally after retrieval.
• IMAP (Internet Message Access Protocol): Another email reading/retrieval protocol that allows users to manage their mail folders on the server, supporting features like searching, marking as read/unread, and multi-device synchronization without necessarily downloading all messages immediately.
• MIME (Multipurpose Internet Mail Extensions): An extension of standard e-mail formats that enables the transmission of non-textual data types such as images, audio files, video clips, and other binary content within email messages.