1 Electronic mail. 2 E-mail: summary The following gives an overview of electronic mail: What it is Using e-mail through the WWW Using e-mail with a dedicated

Download 1 Electronic mail. 2 E-mail: summary The following gives an overview of electronic mail: What it is Using e-mail through the WWW Using e-mail with a dedicated

Post on 29-Mar-2015




4 download

Embed Size (px)


  • Slide 1

1 Electronic mail Slide 2 2 E-mail: summary The following gives an overview of electronic mail: What it is Using e-mail through the WWW Using e-mail with a dedicated e-mail client software Slide 3 3 E-mail: prerequisites Before using e-mail, you should ideally have some knowledge and skills related to computer hardware computer software the Internet the WWW Slide 4 4 E-mail: general description Electronic mail allows network users to send messages to each other by computer. The process is like the postal system in some ways, but in the case of electronic mail, the mail agent is a computer program the address for sending is the address of an electronic mailbox the message is given to the mail system electronically, not on paper the transport system is the data communication network Slide 5 5 E-mail using central, isolated systems E-mail computer E-mail computer 1 A2 B SendRead Slide 6 6 !? Question !? Task !? Problem !? Which problems would be associated with the use of simple, isolated CENTRAL systems and services for e-mail ? Slide 7 7 E-mail using central isolated systems: problems In the case of isolated, central systems, there would be problems: Message senders must have accounts with various e-mail services to address various persons, and analogously, persons who want to receive messages must have accounts with various e-mail services used by the various senders. As one of the consequences, each user should connect with various systems to check if e-mail has arrived in their various mailboxes. Slide 8 8 E-mail: gateways link various systems Gateways solve the problems associated with isolated systems partly, which brings us to store and forward systems, at the other side of the spectrum. Slide 9 9 E-mail using store and forward systems E-mail computer I E-mail computer I 1 A 2 B E-mail computer II E-mail computer II Send Read Slide 10 10 E-mail: examples of global systems Systems with 1 intermediate e-mail computer offering a central bulletin board + gateways to other systems CompuServe (in US), Data-Star (in Switzerland), Dialog (in US), ESA-IRS (in Italy),... Global systems using more than 1 intermediate store and forward e-mail computer + gateways to other systems + decentralised bulletin boards BITNET, Internet SMTP, X-400 network, UUCP network, FidoNet,... Examples Slide 11 11 E-mail: getting started To start, you need: a networked computer a mail system (software) a personal mailbox for you a little know-how e-mail addresses, if you want to send messages... Slide 12 12 E-mail in the Internet One of the most interesting features of the Internet is that virtually every personal computer, minicomputer and mainframe can connect to it in one fashion or another. There are many operating systems in use on the Internet. Nearly every operating system has its own e-mail style. To overcome the mess of competing standards, the Internet has adopted a particular format for e-mail. Based on the RFC (Request for Comments) 822, it is called RFC 822-compliant e-mail. Slide 13 13 E-mail: transfer protocols in the Internet Sending server computer used by Y Receiving server computer B used by X Client microcomputer used by X (with client software = user agent) SMTP Receiving messages, using POP or IMAP Some sending server computer used by X Receiving server computer A used by X SMTP Slide 14 14 E-mail: transfer protocols in the Internet: examples SMTP = Simple Mail Transfer Protocol = communications protocol used most commonly over TCP/IP links in UNIX environments for transport between mail server computers POP = Post Office Protocol IMAP = Internet Message Access Protocol is more powerful than POP; for instance it allows transfer of message headers separately Slide 15 15 E-mail: benefits Overcomes time zone problems inherent to telephone Faster than classical mail International Inexpensive (free of charge in academic institutions) Data are kept in computer readable form Send to more than 1 address in 1 action Easy to include received message in the reply Allows discussion forums & journals based on e-mail... Slide 16 16 E-mail: problems (Part 1) How to know the required e-mail address? Does your contact person have an e-mail address? The time period between sending and arriving of a message is not always known accurately and may be long. How to communicate with users on other systems/networks? (using gateways) You have to learn to use at least 1 e-mail software/system. Differences in user interface among various systems Disk capacity required to store incoming mail Slide 17 17 E-mail: problems (Part 2) The user needs access to a computer Software required to read, store and retrieve the incoming and outgoing messages The user needs some basic understanding of computers and data communication The user may suffer from a lack of time to read and manage the incoming information to answer messages and queries from persons communicating by e-mail Slide 18 18 E-mail: structure of messages Every message in most systems is composed of two basic pieces: The header This contains a series of informative lines which tell the mailing system where to deliver the mail and which provide basic memorandum-like information for the sender and recipient(s). The body This generally consists of free-form text. Slide 19 19 E-mail in the Internet: the header Example: Date:Friday, 26 March 1993; 22:18:45 EST To:atropos@netlab.cis.brown.edu (David B. ODonnell), EL406006@brownvm.brown.edu From:dr_babe@ds9.starfleet.net (Dr. Julian Bashir) Subject:Failed mail to user foo@bar.com? Cc:postmaster@bar.com Example Slide 20 20 E-mail in the Internet: the body The body of e-mail is separated from the header by exactly one blank line. The RFC 822 specification does not state what format the body information must appear in, but the vast majority of e-mail on the Internet today consists of eighty-character- wide lines of ASCII text. Slide 21 21 E-mail addresses of persons (Internet style) An electronic mail address is the string of characters that you must give an electronic mail program to direct a message to a particular person: username@computer-address Examples: (Bitnet: user@indycms.bitnet) Internet U.S.A.: dnoonan@alex.stkate.edu Internet not-U.S.A.: pnieuwen@uia.ac.be Slide 22 22 !? Question !? Task !? Problem !? What is your full personal Internet mail address? Slide 23 23 E-mail: how to find addresses of users? With so many computer systems and users in the world, it is impossible to keep a complete white pages of the Internet. The problem is compounded because people come and go from the net all the time. Storing and updating that much information would be an impossible, daunting task. Nevertheless, several e-mail address directory services can be found by browsing in the WWW. Internet indexes in WWW can also be used to find an address. Slide 24 24 E-mail: reading and managing messages On-line = Linked to the e-mail server computer even when reading and managing messages; for instance: using telnet to login to an e-mail computer using WWW to login to an e-mail computer Off-line ! = On-line only to download messages from the server, and reading and managing messages, NOT linked to the server computer anymore ! Slide 25 25 E-mail: client programs for Unix From a terminal or from a microcomputer emulating a terminal (using for instance telnet), using the software on the Unix-based server: (Line-oriented: mail, mailx,...) Screen-oriented: elm, pine,... Slide 26 26 E-mail client program for Unix: Pine Was developed by the University of Washington Office of Computing and Communications. Is freely available on the Internet via anonymous FTP. Is designed for ease-of-use with the novice computer user in mind. Is based on Internet mail protocols (e.g. SMTP). Was originally based on Elm, but has evolved much since. *---Example Slide 27 27 E-mail client program for Unix: Pine: features Shows a message summary which includes the status, sender, size, date and subject of messages. Can view and process mail with the following commands: forward, reply, save, export, print, delete, capture address and search. Offers on-line help specific to each screen and context. Is very portable and runs on a variety of UNIX machines (including DECstation, NeXT, VAX and Sun). *---Example Slide 28 28 E-mail client program for Unix: Pine: ease of use The guiding principles for achieving ease-of-use in Pine were: careful limitation of features one-character mnemonic commands always-present command menus immediate user feedback high tolerance for user mistakes It is intended that Pine can be learned by exploration rather than reading manuals. *---Example Slide 29 29 E-mail through the WWW: international systems Some international systems based on the WWW allow you to send and read/receive e-mail messages. Examples: Hotmail of Microsoft, Webmail of Netscape = Net@ddress, Yahoo Mail Some international systems based on the WWW allow you to receive/read the messages from the POP mail account provided by your ISP. Example: Yahoo Mail Slide 30 30 E-mail through the WWW: local systems In many institutes, local systems restricted to users of the institute, offer services related to e-mail based on the WWW. Example: at the universities in Brussels: http://www.ulb.ac.be/tools/webmail.html http://www.ulb.ac.be/tools/webmail.html Slide 31 31 !? Question !? Task !? Problem !? What are the advantages and disadvantages of e-mail through the WWW, in comparison with other systems? Slide 32 32 E-mail through the WWW: advantages Available from any WWW browser, and thus suitable when traveling. Client software dedicated to e-mail on your microcomputer is not required. Your e-mail address on a public system may be more stable, may last longer, than an e-maill address provided to you by the institute where you study or work. Slide 33 33 E-mail through the WWW: disadvantages (Part 1) Uses the network inefficiently, when the sender and th


View more >