Email Protocols (original) (raw)

Last Updated : 11 Apr, 2026

Email protocols are standardized rules that control how emails are sent, received, and accessed between mail clients and mail servers over the Internet.

• Enable communication between sender and receiver.
• Define how mail servers and email clients interact.
• Ensure reliable email delivery and access.
• Commonly used in services like Gmail and Outlook.

**Note: Email protocols establish communication between the sender and receiver for the transmission of email. Email forwarding includes components like two computers sending and receiving emails and the mail server.

Types of Email Protocols

Three basic types of email protocols involved for sending and receiving mails are:

1. SMTP (Simple Mail Transfer Protocol)

Simple Mail Transfer Protocol is used to send mails over the internet. SMTP is an application layer and connection-oriented protocol. SMTP is efficient and reliable for sending emails. SMTP uses TCP as the transport layer protocol. It handles the sending and receiving of messages between email servers over a TCP/IP network.

Simple Mail Transfer Protocol

• Sends emails from sender to receiver using mail servers.
• Uses commands like HELO, MAIL FROM, RCPT TO, DATA to transfer messages.
• Identifies sender and receiver email addresses during communication.
• Notifies sender if email delivery fails.
• Considered reliable due to error reporting.

2. POP3 (Post Office Protocol)

Post Office Protocol is used to retrieve email for a single client. POP3 version is the current version of POP used. It is an application layer protocol. It allows to access mail offline and thus, needs less internet time. To access the message it has to be downloaded.

Post Office Protocol 3

• POP allows only a single mailbox to be created on the mail server.
• POP does not allow search facilities
• Some of the POP commands are LOG IN, STAT, LIST, RETR, DELE, RSET, and QUIT.

3. IMAP (Internet Message Access Protocol)

Internet Message Access Protocol is used to retrieve mails for multiple clients. There are several IMAP versions: IMAP, IMAP2, IMAP3, IMAP4, etc. IMAP is an application layer protocol. IMAP allows to access email without downloading them and also supports email download.

Internet Message Access Protocol

• The emails are maintained by the remote server. It enables all email operations such as creating, manipulating, delete the email without reading it.
• IMAP allows you to search emails. It allows multiple mailboxes to be created on multiple mail servers and allows concurrent access.
• Some of the IMAP commands are: IMAP_LOGIN, CREATE, DELETE, RENAME, SELECT, EXAMINE, and LOGOUT.