Today’s one of the most admired network service “E-mail” has been modernized the concept of how to communicate worldwide with simplicity and speed without spending extra money. However, to run this service on a computer system or any other end device, e-mail is needed some specific applications as well as services such as application layer protocol “Post Office Protocol” (POP).
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But the Post Office Protocol and the Post Office Protocol (version 3) are bounded for as the e-mail deliverance protocols and are best known usual protocols for the client/server environment. These two protocols can transport e-mail from server to the client (Mail user agent). And a Mail User Agent (MUA) application is used to compose the email messages. But two types of configuration for the e-mail service usage (such as to configuring the e-mail clients) you may be required either IMAP e-mail or POP e-mail client configuration. Although, standard SMTP (Simple Mail Transfer) protocol, in the internet world, is used to send e-mail but POP protocol can be used just to retrieve the e-mails.
POP is designed for the application-layer in order to be used as a local electronic mail service for the clients who want to retrieve the messages in the form of e-mails from a remote server via a TCP/IP link or connection. This protocol is endowed with absolute and intricate remote right of entry to the usual mailbox processes. But in case of POP clients, problem such as downloading of the same message many times may occur by the e-mail clients. Likewise, POP clients in general are connected to the mail server thus to get back all the messages, and to store up them on the user computer. After that, deletion of these messages is performed on permanent basis from the server. At last, connection sever is done.
But on the other hand, many Post Office Protocol clients are having the right of leaving the e-mail messages existed on the server even after downloading them. In other words, e-mails are not going to be deleted from the e-mail server after their retrieval by the client. This trait in certain situation is really proved very valuable. POP3 server is listened in via port 110. It supports safe and secure messaging with the help of mail server through the port 995. But with the e-mail protocol POP, certain tasks like friends & family contacts and appointments can’t be handled.
Anyway, the POP is planned for the application-layer of OSI layered suite and is being used by the local e-mail clients for the retrieval of e-mails from a server. But current version 3 of this protocol is recognized as POP3 which is almost supported by the every webmail service including g-mail and yahoo services. You can say that the oldest two internet message access protocols are POP3 and the POP. Purpose of both is to support the “offline” but limited e-mail processing. When e-mails are distributed to the e-mail server then a far-flung e-mail client from time to time downloads messages from that e-mail server to the user computer.