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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.
POP3
POP stands for Post Office Protocol. It is generally used to support a single client. There are several
versions of POP but POP3 is the current standard version.
22 Touchpad Computer Applications-X

