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Table of contents
What Is POP Protocol?
How Does The POP Protocol Work?
Versions Of POP protocol
How does POP3 Work?
Advantages of POP3
Disadvantages of POP3
POP Commands
Frequently Asked Questions
How can you make POP3 secure?
Can Gmail use POP3 or IMAP?
What is the relationship between POP3 and IMAP?
Write some functions of the POP Protocol.
Last Updated: Mar 27, 2024

POP Protocol

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Protocols are also necessary for email. Every time an email is sent or received, specific protocols ensure delivery or receipt of the message. The most common email protocols are MIME, POP3, SMTP, and IMAP. 

We will discuss POP3 here. This protocol assumes that messages can be read offline rather than just relying on an online network.

What Is POP Protocol?

Receivers can retrieve email from remote servers and store it on their local machines using Post Office Protocol (POP). It is common for POP email messages to be automatically deleted on the server after successfully being transferred to the recipient's system, although this can sometimes be changed. Users can authenticate themselves and modify their mailboxes.

As well as POP, MIME supports email attachments, which is an important standard for internet messages. A POP account will work best if the user does not permanently connect to the internet or other networks containing email servers.

Users download mail from their inbox to their local PC or MAC machine using POP as an "offline" protocol. Mail servers cannot manage or manipulate folders or messages using the POP protocol.

How Does The POP Protocol Work?

There are many other protocols for accessing emails like IMAP and SMTP, so why use the POP protocol?

It is because POP supports offline access to messages. When the sender sends online mail, the sending and receiving are done with the help of SMTP through the internet, but when we are sending mail from one computer to another and receiving client is offline, the mail is stored on the pop server. As soon as the client gets online, this POP server sends the mail to the client.

illustration image

POP has the following problems: 

  • The search facility is not available.
  • You can only create one mailbox on the server.
  • Messages must be downloaded in order to be accessed.
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Versions Of POP protocol

In 1984, the Internet Engineering Task Force published RFC 918, the first version of Post Office Protocol. There was a need for a simple and efficient way to retrieve emails from a server. In contrast to online access, they found it more convenient to read emails offline.

It was RFC 937 that first published version 2 of Post Office Protocol in 1985, which was then replaced by RFC 1081 in 1988 with version 3. Over the next ten years, POP3 was revised several times before becoming the standard today.

While POP3 has been enhanced and refined several times. Its developers have kept the basic principle of an efficient three-stage protocol i.e Sender - Server - Receiver for retrieving mail from a server to a client, since it is popular due to its simplicity.

How does POP3 Work?

POP3 uses two ports by default:

  • There is a default non-encrypted port 110 for POP3.
  • If you want to connect to POP3 securely, you need to use port 995.

The user will connect to the POP3 server when checking for a new email. Upon connecting, the email client will supply the server with credentials to authenticate. To retrieve all email messages, the client uses text-based commands. Once the messages are downloaded, they are stored as new emails on the user's local system. The server copies are then deleted, and the connection is cut off.

After a server email is retrieved, it is automatically deleted. The email is thus tied to a specific machine and cannot be accessed from another machine's email client. To rectify this issue, the user can configure the email client settings to leave a copy of the emails on the server.



Advantages of POP3

  • The user can download emails to their computer. 
  • The user can read messages while offline.
  • The attachments are already downloaded, so opening them is quick and easy.
  • Emails are stored on the local machine, saving space on the server.
  • Emails can only be stored on your hard drive if large enough.
  • Quickly configured and used, very popular.


Disadvantages of POP3

  • You cannot access your emails from another computer unless this option is set.
  • A local email folder cannot be exported from one email client to another.
  • If a folder becomes corrupt, the entire mailbox can be lost.
  • If the user opens an email attachment and their virus scanner doesn't detect it, they might be exposed to viruses that may harm their PC.


You can read related articles such as Congestion Control in Computer Networks here.

POP Commands

You can use some basic commands in POP:

  • LOGIN: The connection will be opened using this command.
  • STAT: This command is used to display the number of messages which are currently present in the mail Box.
  • LIST: This command shows the summary of messages in the mailbox.
  • RETR: This command is used to access the messages.
  • DELE: This command is used for deleting the messages.
  • RSET: This command is used for resetting the session.
  • QUIT: It is used for Logging off the session.

You can also read about mime protocol,Locked based protocol in DBMS

Frequently Asked Questions

How can you make POP3 secure?

Using POP3, you can read or save your emails online or offline; however, you can delete your messages after reading them. You can make POP3 more secure by using an encrypted connection through STLS, TLS, or SSL.

Can Gmail use POP3 or IMAP?

Integrating the Gmail service with email software on a computer or mobile device using the IMAP and POP mail servers is possible. In contrast, some free email applications offer only a POP email service. Most premium and free email applications offer both IMAP and POP email compatibility.

What is the relationship between POP3 and IMAP?

Most email clients and website servers support IMAP, just like POP3. IMAP is better suited to users who work with various devices or wish to access email from multiple locations than POP3. POP3 uses port 993, IMAP uses port 143. POP3 or IMAP are used for accessing the message when the mail has been received by the recipient.

Write some functions of the POP Protocol.

Some functions are:
→ The user is not notified that a new message has arrived. Instead, the messages are stored at the server until the user retrieves them
→ POP examines the message's in the first few sentences before retrieving them to determine whether it is worth retrieving.


In this blog, we have learned what POP Protocol is, how do this works, and the POP versions. After that, we saw the difference between POP and POP3 and some advantages and disadvantages. 

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