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Downloading and Uploading
                  Downloading refers to transfer of file from a remote computer to the host computer. FTP helps to make
                  a directory on a computer connected to the Internet and to transfer a file from that directory on another
                  computer on the Internet.

                  The files can be downloaded from a FTP site even by an anonymous user. To download, the browser asks
                  for a name and location on the local computer to save that file.
                  Uploading refers to the transfer of a file from the host computer to a remote computer/server. Uploading
                  files is usually not possible with anonymous FTP. Anonymous FTP is used primarily to help in downloading
                  a particular directory of files. Anyone can download files from the directory but only the administrator can
                  upload the files to the directory.

                    E -MAIL PROTOCOLS

                  E-mail Protocols are a set of rules that help the email client to properly transmit the information to or
                  from the mail server. Let’s discuss different e-mail protocols like. SMTP, POP and IMAP.

                  SMTP

                  SMTP stands for Simple Mail Transfer Protocol. It is a TCP/IP protocol that is used in sending and receiving
                  e-mail. Simple Mail Transfer Protocol is also known as RFC 821 and RFC 2821.
                  It is a standard protocol used for sending an e-mail efficiently and reliably over the Internet. However,
                  SMTP is limited in its ability as its purpose is to only queue messages at the receiving end. POP3 or
                  IMAP saves messages in a server mailbox and enables them to download them periodically from the
                  server.


                          MTA/e-Mail Client                                                  Recipient e-Mail Server

                                                            SMTP




                                SMTP                                           Queue Messages









                  When a user sends an e-mail, it is sent to the e-mail server or Mail Transfer Agent (MTA) which further
                  contacts the recipient e-mail server using SMTP client. These SMTP commands specify the sender’s and
                  receiver’s e-mail address, along with the message to be sent. The exchange of commands between servers
                  takes place without intervention of other users. In case, message is not delivered, an error report is sent
                  to the sender. It makes SMTP a reliable protocol.

                       Do you know?

                       SMTP is usually implemented to operate over Internet port 25. Many mail servers now support Extended
                       Simple Mail Transfer Protocol (ESMTP), which allows multimedia files to be delivered as e-mail.




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