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POP Protocol

In this tutorial, we will be covering the concept of POP which is another Application layer protocol.

POP is a short form of Post Office Protocol. It is another protocol present at the Application Layer of the OSI reference model.

  • POP is mainly a message access protocol.

  • POP is basically an internet standard protocol and as we already told you it works on the application layer and is used by the local email software in order to retrieve emails from the remote email server over the TCP/IP connection.

  • The Post office Protocol (POP) does not allow any search facility.

  • This protocol mainly allows one protocol to be created on the server.

  • As this protocol supports offline access to the messages and so less internet usage time is required by this.

  • Non-email data is not accessed by this protocol.

  • Some of the common clients that make use of POP3 are Gmail, Netscape, Internet Explorer, Eudora.

History of POP

The POP(post office protocol) was published in 1984 by Internet Engineering Task Force. After that, it has been updated two times, because the backend developers want to make the layout simple.

The second version of POP was developed in 1985 and known as POP2 and this version needs the SMTP protocol in order to push the emails.

Then after the third version of POP was released in 1988 and known as POP3, this version does not require the SMTP protocol. The POP(Post office protocol version 3) is also integrated into famous e-mail software, like Eudora and Outlook Express.

And since then(1988) the POP3 is the active version.

Working of POP

All the incoming messages are stored on the POP server until the user login by using an email client and downloads the message to their computer. After the message is downloaded by the user it gets deleted from the server.

As we know that the SMTP is used to transfer the email message from the server to the server, basically POP is used to collect the email with an email client from the server and it does not include means to send messages.

If any user tries to check all the recent emails then they will establish a connection with the POP3 at the server-side. The user sends the username and password to the server machine for getting the proper authentication. After getting the connection, users can receive all text-based emails and store them on their local terminal (machine), then finally discard all server copies and then breaks the connection from the server machine.

In order to retrieve a message from the server following steps are taken;

  • Firstly a TCP connection is established by the client using port 110.

  • The client identifies itself to the server.

  • After that client issues a series of POP3 commands.

The above figure indicates the exchange of Commands and responses in the POP3

Features of POP protocol

Given below are some of the features provided by the POP protocol:

  • The POP protocol uses PORT 110.

  • It makes the use of a Persistent TCP connection.

  • It is a Pull protocol.

  • It is a connection-oriented protocol.

  • The POP protocol is a stateful protocol until the mail is downloaded and across the sessions, it is a stateless protocol.

Let us now take a look at the commands of POP :

Commands Description
LOGIN This command is used to open a connection
STAT This command is used to display the messages that are currently in the mailbox.
DELE This command is used to delete a message.
RSET This command is mainly used to reset the session to its initial state.
QUIT This command is used to log off the session.
LIST This command is mainly used to get the summary of each message where each message summary is shown.
RETR This command is mainly used to select a mailbox in order to access the messages.

Advantages of POP

Given below are the advantages offered by the POP :

  • This protocol does not require any internet connection in order to access the downloaded emails.

  • In order to receive emails on a single device, POP3 is very useful.

  • The Configuration of this protocol is simple and it is easy to use.

  • Less storage space is needed in order to store emails on the hard disk.

  • This protocol is much better for the ones who hardly check their email on any other computer.

Disadvantages of POP

Now it's time to take a look at the drawbacks of Post office Protocol(POP):

  • The same email account cannot be accessed from multiple computers or devices.

  • The spread of the virus is easily using this protocol because it is possible that the file attached with the email contains the virus.

  • The transfer of the local email folder to another email client terminal point is a difficult task.