In this article I describe the POP3 Post Office Protocol in computer network for CCNA Exam. POP3 Post Office Protocol provide to access or retrieve the email messages form mail server. A client can receive the email messages from mail server via using the POP3 Post Office Protocol. POP3 Post Office Protocol works between the client and the mail server on internet. Some private organizations uses their own private mail services on the intranet. I mean to say the mail server and client communicate over the internet but in the way of intranet. Before going to learn about the POP3 Post Office Protocol let’s take a look on some basic terms related to email services.
History or Email
According to some computer magazines and other resources, the first email was sent from one computer to another computer in 1971. The engineer who supposed to be sent first email was RAY TOMLINSON. Before this event an user can sent the message within a single machine with some standalone applications. After the mail sent within different machines the email creates a revolution in the field of Information Technology. Now there are many email servers available like Microsoft exchange server, IBM’s Lotus and many other of Linux version.
The Email system in computer network or internet
Email is generally pronounced in place of electronic mail. An Email provide to share text, graphics, audio and video from a user to another user on internet. Approx. 80% people around the world works on email on internet. People use email to send personal information as well as official information on internet. Email services provided by some particular Email servers for clients. The clients are the users created in email servers to provide the email services. The connectivity between the clients and mail server may be on internet or intranet.
An email can be configured on a domain name with prefix the email address for example user_name@domain_name. multiple protocols required to float an email address from sender to receiver. The main protocols are IMAP, SMTP and POP which are used for floating the email on a network. In this article our focus is on IMAP which is used to receive the emails from mail servers.
Email servers in mail services
Email servers are liable to receive, forward, deliver and store the emails between the email users. The email message can be downloaded by the clients or a client can access the email messages from the mail server on browser based. The email server deliver the mail to the recipient, in case the recipient is not available, the mail server notify the mail sender about the failure of delivery of email. Mail servers are generally of three types SMTP servers, POP servers and IMAP servers. All three severs have different kind of works. Forwarding and receiving of email are depends on the email services.
Email Clients in mail services
Email clients related to the user who is using the email service. Actually the email client is a software which is configured to receive the email and restore the mails in it. A user can see the emails by just opening the email client software. The examples of mail clients are thunderbird, outlook etc. All smart phone provide a facility to configure the mail server. The email server provides the data so a user can configure his smart phone as email client. What happens now, when the smart phone get internet connection the mail application receive the email from the mail server. The user can read the mails any time once after the email received by the mail application.
Web-mail interface for email
The webmail interface allow a user to access the email account from a browser of a computer or smartphone. The computer or smart phone must be connected to the network or internet. The email appears and can be forwarded till the browser is open. Once the browser closed the email access is vanished. So this is the most common technique via which most of email users access their mail accounts from the internet. Later in this article i describe the protocols used when a client access the email from a browser of a computer.
Protocols used for email service
There are three protocols used for email service on the internet POP3 Post Office Protocol, IMAP and SMTP. SMTP protocol use to send the email while remaining two POP3 and IMAP used to retrieve or receive the email from the mail server.
POP3 Post Office Protocol allow to download the email in a computer client or smart phone. After downloading the email the mail server delete the delivered emails. So by using POP3 Post Office Protocol a user can read the emails only on a single device. Once the email downloaded into the mail client the mail automatically deleted from the mail server. POP3 Post Office Protocol works on port 110 and 995.
Port 110 used for unsecured like HTTP and 995 is used for secure mail communication like HTTPS. POP3 Post Office Protocol saved the emails in mail server’s single mailbox. The saved email sent to the user when mail client opens. If you want to access your email form one machine and the machine have a lot of space, then POP3 protocol is useful to you. POP3 Post Office Protocol doesn’t support multiple device for same user.
SMTP protocol provide the feature to send the email from one client to another client over the internet. SMTP works on port 25, 2525 and 465. Port 25 and 2525 works to send the email without encryption and port 465 used to send the email securely on internet or WAN.
IMAP Internet Message Access Protocol is another protocol to retrieve the emails from the mail server. Mostly the IMAP Internet Message Access Protocol allow to access the email on browser based access from a computer or client. The difference of IMAP from POP3 Post Office Protocol is that IMAP allow to access the emails from different applications and clients. Hence a user can access his email from multiple device and applications when using the IMAP Internet Message Access Protocol. Now lets see the POP3 Post Office Protocol in brief.
POP3 Post Office Protocol explained
POP3 Post Office Protocol is similar to IMAP Internet Message Access Protocol. The Post Office Protocol is use for receiving mail message on mail client from email server over the internet or WAN. Post Office Protocol used to transfer the mail message from mail server to mail client. POP3 provides the facility to the mail client to view and download the messages. Once message downloaded to mail client the mail messages automatically delete from mail server. POP3 protocol doesn’t allow mail client to organize the messages in the mail server. POP3 Post Office Protocol does not allow to receive the emails for multiple applications or clients.
IMAP protocol provide the facility of organize the message in mail servers from the client end. That’s why mostly mail client configured to IMAP instead of POP3. POP3 Post Office Protocol supports only one mail client at a time. If another client tries to connect with mail server over POP3 which is already connected, then the mail server denies the new request. POP3 Post Office Protocol provides only single mailbox to the mail client so when you need to keep the mail personal configure the email client with POP3 Post Office Protocol.
POP3 sent the mail message to the client when it is activated. We can say when a client is available on internet the Post Office Protocol receives the emails. Later the user can see the mails offline. Mail client examples are Microsoft Outlook and thunderbird. Post Office Protocol doesn’t support multiple devices for the same user
POP3 Post Office Protocol vs IMAP Internet Message Access Protocol
IMAP Internet Message Access Protocol provides access to email from multiple devices. This feature is helpful to user to use the email from multiple devices at a time. Suppose a user using the desktop outlook and same time want to access the email from his smart phone. This facility can be provided by IMAP protocol only. IMAP Internet Message Access Protocol is used by email clients to retrieve email from a mail server over a TCP/IP connection.
Post Office Protocol allow to access the emails from a single client only. After delivery of the email the mail messages deleted from the mail server. So it is not possible to access the emails from multiple devices or applications at a time by using Post Office Protocol. POP3 Post Office Protocol uses port 110 on a network to retrieve the email message from mail server. POP3 Post Office Protocol secure uses 995 port on a network.
Connections of mail client and mail server over POP3 Post Office Protocol
Mail clients are applications developed for email management only. Example of mail client is MS outlook and thunderbird. Mail clients connected with mail server if the mail client interface is active. The connection is disconnected when the mail client downloads the message from mail server. Every time when a mail client become active new connection created between the mail client and mail server over the Post Office Protocol.
In MS Outlook the notification of connected is always remains until the application is not closed by the user. The Post Office Protocol allow the currently connected client to access the mailbox in mail server. No any other mail client can create a connection with mail server when POP3 connection is established once. IMAP Internet Message Access Protocol allow more than one connection at a time. Multiple mail clients can connect with mail server using IMAP protocol.
With POP3 setup mail message automatically deleted form mail server after downloading to mail client. This feature provides the facility of only one mail client can connect at a time.
Email message status notification
There are many codes defines to indicate the status of email message. These codes are known as flags. Message state means read receipt, deleted, replied, saved, sent successfully etc. A client can check the status of any email message pertaining to him. Only IMAP protocol have this feature. POP3 doesn’t have any message status notification feature.
In this article I describe the POP3 Post Office Protocol in computer network for CCNA Exam. I hope you found this article helpful for CCNA exam. For any query or suggestions you may drop a comment below or contact us. Your suggestions are always welcome by us.
