SMTP vs POP: Difference and Comparison

The term ‘email protocol’ stands for a standard way to exchange information between email service providers (like Outlook, Gmail, etc.) and email clients (like Apple Mail, Thunderbird) and vice versa. Various email protocols provide different functions, like transporting emails and sending emails. SMTP and POP are also email protocols.


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Key Takeaways

  1. SMTP (Simple Mail Transfer Protocol) handles sending and relaying email messages between servers.
  2. POP (Post Office Protocol) retrieves and downloads email messages from a mail server to a local device.
  3. Both protocols are essential for email communication, with SMTP handling outgoing mail and POP managing incoming mail.


SMTP sends email messages from a client to a server, while POP retrieves email messages from a server to a client. SMTP is a push protocol, meaning that the client initiates only the communication. POP is a pull protocol, meaning the client initiates both the communication and new email requests.


The full form of SMTP is Simple Mail Transfer Protocol. It is an email protocol used to send mail to any person on the Internet. It is used twice while sending mail:

  1. Between the sender(client) and the client’s mail server
  2. Between the client’s and receiver’s mail server

The full form of POP is Post Office Protocol. Its main use is to retrieve emails from the receiver’s mail server. It is used between the receiver and its mail server. The use of this protocol allows the receiver to open the mail even in offline mode.

Comparison Table

Parameters of ComparisonSMTPPOP
DefinitionIt is a protocol that sends email across networks based on MTAs to transfer the mail to the right computer.It’s work is like a post office clerk, it receives and stores mails.
UseIt is used to send messages.It is used to access messages.
Ports it works onIt works on Port 25.It works on Port 110
Number of times it is impliedTwice(Between the sender(client) and the client’s mail server; and  the client’s and receiver’s mail server)  Once( Between the receiver and its mail server)
Another nameIt is also known as PUSH protocol.It is also known as PULL Protocol

What is SMTP?

Simple mail transfer Protocol (SMTP) is a very reliable protocol for transferring emails in bulk on the internet. Since the eighties, it has successfully transferred mail. It has, hence become the standard for sending out mail worldwide.

The transfer of mail between Server MTA and Client MTA(Mail Transfer Agent) takes place in three steps: establishment of connection(between server MTA and client), transfer of mail (to the various recipients), and termination of connection by the client(on the successful transfer of messages).

However, the use of this protocol is not free from issues. Spam mail is a major issue. It floods the recipient’s mail with a lot of useless content. Moreover, various computer viruses also get transferred alongside. Security concern is another noteworthy issue with SMTP. Various ways had been found to solve the issue, but it wasn’t of much help.

Companies use this server for marketing via mail and automatic transactional emails such as password changes, purchase confirmations, etc.

What is POP?

Post Office Protocol is a standard way to access mail on our computers and use our mailboxes at our convenience. It is the incoming server. POP3, which uses port 110, is the latest version of POP.

After SMTP has successfully delivered the mail to the server MTA( Message Transfer Agent), the POP protocol pulls it from the last position.  To open mails from client MAA( Message Access Agent), a username and password are needed to establish a connection. Once it is established, mails can be retrieved.

All emails get downloaded from the server and remain accessible even when offline. Messages get stored on the computer of the user, removing them from the email server.

This protocol works in two modes: keep and delete mode. The first mode is used when the user is using someone else’s compute. Emails remain there for later use on his permanent computer. The second mode is used while working on his permanent computer. Mails get deleted from the mailbox and are saved on his computer for later use.

It was first made to access(in the eighties) and delete mail in places where the internet was not accessible smoothly. When the user gets online, the messages get delivered.

Main Differences Between SMTP and POP

  1. SMTP acts as a Message Transfer Agent to transfer emails to the right computer server. On the other hand, POP acts as a Message Access Agent for accessing mail.
  2. SMTP is used on Port 25, whereas POP is used on Port 110.
  3. SMTP is a Push Protocol, whereas POP is a Pull protocol to pull messages from the receiver’s server.
  4. SMTP is the Outgoing server which ensures that messages reach the right destination. On the other hand, POP is the incoming server .
  5. SMTP is implied twice. It transfers the message to the receiver’s mailbox present on its server. POP is implied once to retrieve mails from the receiver’s server on its computer.
Difference Between SMTP and POP
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