BY SAGAR SINHA SAPTARSHI BAKSHI SARTHAK JAIN SHAILZA CHAUDHARY POP3 & FTP BY SAGAR SINHA SAPTARSHI BAKSHI SARTHAK JAIN SHAILZA CHAUDHARY

Introduction The first and the second stages of mail delivery use SMTP. However, SMTP is not involved in the third stage because SMTP is a push protocol; it pushes the message from the client to the server. In other words, the direction of the bulk data (messages) is from the client to the server. On the other hand, the third stage needs a pull protocol; the client must pull messages from the server. The direction of the bulk data are from the server to the client. The third stage uses a message access agent(POP3 and IMAP)

POP 3(Post Office Protocol Version 3) It is a message access agent. protocol for receiving e-mail client/server protocol achieves transparent connection between email server and e-mail client POP3 is simple and limited in functionality. It is a pull protocol; the client must pull messages from the server.

Modes of POP 3 Pop3 has two modes: keep mode and delete mode In delete mode mail is deleted from mailbox after each retrieval. In keep mode, mail remains in mailbox after each retrieval.

Stages of mail delivery There are 3 stages in Mail Delivery: The first and the second stages of mail delivery use SMTP( push messages) The third stage of mail delivery use POP3 or IMAP4(pull messages)

Advantages Simple protocol Easier to implement Disadvantages Simple protocol Easier to implement Copies all messages when connection is made. Don’t allow user to organize mails on server. Don’t allow user to partially check the contents of mail before downloading.

IMAP 4(INTERNET MAIL ACCESS PROTOCOL) As its name implies, IMAP allows us to access email messages wherever we are . Basically, email messages are stored on servers. Whenever we heck inbox, our email client contacts the server to connect with messages. When we read an email message using IMAP, we aren't actually downloading or storing it on computer; instead, we are reading it off of the server. As a result, it's possible to email from several different devices without missing a thing.

It as an intermediary between email client and email server. When you sign into an email client like Microsoft Outlook, it contacts the email server using IMAP. The headers of all of your email messages are then displayed. If you choose to read a message, it is quickly downloaded so that you can see it - emails are not downloaded unless you need to open them.

POP VS IMAP4 If we decide to check email from a different device, the messages that have been downloaded previously will not be available. POP works fine for those who generally only check their email messages from a single device; those who travel or need to access their email from various devices are much better off with IMAP-based email service. Unlike POP, IMAP allows us to access, organize, read and sort email messages without having to download them first. IMAP does not move messages from the server to computer; instead, it synchronizes the email that's on computer with the email that's on the server. As a result, IMAP is very fast and efficient.

FILE TRANSFER PROTOCOL(FTP) FTP (File Transfer Protocol) is the simplest and most secure way to exchange files over the Internet. Transferring files from a client computer to a server computer is called "uploading" and transferring from a server to a client is "downloading". To access an FTP server, users must be able to connect to the Internet or an intranet (via a modem or local area network) with an FTP client program. Some commonly used FTP clients include Filezilla, FireFTP etc.

FTP differs from other client/server applications in that it establishes two connections between the hosts. One connection is used for data transfer, the other for control information (commands and responses). Separation of commands and data transfer makes FTP more efficient. The control connection uses very simple rules of communication. The data connection, on the other hand, needs more complex rules due to the variety of data types transferred. FTP uses two well-known TCP ports: Port 21 is used for the control connection, and port 20 is used for the data connection.

The control connection remains connected during the entire interactive FTP session. The data connection is opened and then closed for each file transferred. It opens each time commands that involve transferring files are used, and it closes when the file is transferred. In other words, when a user starts an FTP session, the control connection opens. While the control connection is open, the data connection can be opened and closed multiple times if several files are transferred.

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