Difference between SMTP and POP3


SMTP and POP3 are message protocols which are required for sending and receiving the messages between the mail servers. In this article, we are going to compare and contrast the various features of SMTP and POP3 based on the tasks for which these two protocols have been designed.

What is SMTP?

The Simple Mail Transfer Protocol (SMTP) is an Internet communication protocol for sending and receiving electronic mail. SMTP is used to transmit and receive mail messages by mail servers and other message transfer agents.

User-level email clients usually utilize SMTP exclusively to transmit messages to a mail server for relaying, and send an outgoing email over port 587 or 465, as defined by RFC 8314.

IMAP (which superseded the earlier POP3) is the standard for retrieving messages, however proprietary servers, such as Exchange ActiveSync, sometimes employ proprietary protocols as well.

SMTP has been upgraded, changed, and expanded several times since its inception in 1981. The current version of the protocol is flexible, including additions enabling authentication, encryption, binary data transmission, and internationalized email addresses. The Transmission Control Protocol (TCP) is frequently used by SMTP servers on ports 25 (plaintext) and 587 (encryption) for encrypted communications.

What is POP3?

The Post Office Protocol allows a user client programme to connect to a mailbox on a mail server through an Internet Protocol (IP) network. Messages may be downloaded and deleted via the protocol.

POP3 clients connect to the server, retrieve all messages, save them on the client computer, and then delete them. The necessity for users with only brief Internet connections, such as dial-up access, to be able to retrieve e-mail when connected, and then read and edit the obtained messages when offline, drove the creation of POP and associated protocols.

POP3 clients also have the option of leaving messages on the server after they have been downloaded. The Internet Message Access Protocol (IMAP), on the other hand, was designed to leave all messages on the server in order to allow management of different client applications and to enable both online and offline modes of operation.

Difference between SMTP and POP3

The following table highlights the major differences between SMTP and POP3 −


Simple Mail Transfer Protocol (SMTP) is a part of the application layer of the TCP/IP protocol which is primarily used by following a process called "store and forward".

SMTP moves email on and across networks based on Mail Transfer Agent (MTA) to send communication to the right computer and email.

Post Office Protocol 3 (POP 3) is a protocol used for receiving email.

Much like the physical version of a post office clerk, POP3 receives and holds email for an individual until they pick it up.

Designed SMTP is designed for sending the mails. POP3 has been designed for receiving the mails.
Implementation SMTP is implemented technically and physically on port number 25 of the system. POP3 is implemented on port number 110.
Type SMTP acts as a MTA (Message Transfer Agent) for sending the message to the receiver. POP3 is a MAA (Message Access Agent) for accessing the messages from mail box.
Target Usage SMTP transfers the mail from sender’s computer to the mail box present on the receiver's mail server. POP3 allows to retrieve and organize mails from mailbox on receiver mail server to receiver's computer.


SMTP transmits mail from the sender's computer to the recipient's mail server's mailbox. It's a Message Transfer Agent (MTA) that sends the message to the recipient.

POP3 allows you to obtain and manage emails from the recipient's inbox on the recipient's computer. It's a Message Access Agent (MAA), a program that allows you to read messages from your inbox.

Updated on 04-Aug-2022 08:26:39