• What is an E-Mail?
• How it works?
• Types of Protocols
• Mail Clients
• Question & Answers
What is e-mail?
• Electronic mail, most commonly referred to as email or e-mail.
• It is a method of exchanging digital messages from sender to one or more
• Early email systems required both the sender and receiver should be online,
now that is called as “Instant Messaging.”
• Today’s email system is based on a “Store-and-forward” model.
• It consists of 3 parts:
i) Sender and Recipient address
ii) Subject line
• Simple Mail Transfer Protocol (SMTP)
• Internet Message Access Protocol (IMAP)
• Post Office Protocol 3 (POP3)
• SMTP (Simple Mail Transfer Protocol):
It is a connection-oriented, text based protocol, communicates with a mail
sender and mail receiver by issuing commands.
SMTP transaction consists of 3 commands:
i) MAIL command, to establish the return address i.e., sender
ii) RCPT command, to establish a recipient of the message.
iii) DATA to send the message .
SMTP Server connects to by looking up the MX (Mail Exchange) DNS
resource and connects to it.
SMTP uses TCP port 25
• Internet message access protocol (IMAP) is a protocol for e-mail
• IMAP server listens on well-known port 143.
• IMAP is an Application Layer Internet protocol that allows an e-mail client
to access e-mail on a remote mail server.
• E-mail clients using IMAP generally leave messages on the server until the
user explicitly deletes them.
• Incoming e-mail messages are sent to an e-mail server that stores messages
in the recipient's e-mail box. The user retrieves the messages with an e-mail
client that uses one of a number of e-mail retrieval protocols.
• Post Office Protocol 3 (POP3) is a protocol for e-mail retrieval.
• POP3 is an application-layer Internet standard protocol used by local e-mail
clients to retrieve e-mail from a remote server over a TCP/IP connection.
• POP supports simple download-and-delete requirements for access to
• A POP3 server listens on well-known port 110.
Locally installed Clients:
• Microsoft Outlook
• Mozilla Thunder Bird
• IBM Lotus Notes
Web based Mail Clients:
• Yahoo Mail