UNIT 4











Electronic mail-   
Introduction-   email is a method of sending messages, voice, video and graphics over digital communication link such as the internet anywhere in the world at very cost effective rate. Technically e mail is a type of client server application that provides a routed, stored message service between any two email accounts.  Because all modern computers can be connected to the internet user can sent email over the internet to any location all over the world.

Email network’s and server’s – the primary component of the electronic mail system is a “post office’” which is an area on the shared hard disk that is reserved for mail. This post office serves as the central message holder and has in and out baskets for each user. To send a message, a link is established between the sender’s out basket and the receiver in basket.
 














Working of the email on the internet-email is the most heavily used feature of the internet. You can use it to send messages to anyone who is connected to the internet or to a computer network that has a connection to the internet. Email message are sent in the same way as most internet data. The TCP protocol breaks messages into packets. It protocol deliver’s the packets to the proper location and then TCP reassembles the message on the receive end so that it can be read. When you send email to someone on the internet that send email to someone on the internet that message has to travel throw a series of networks before it reaches to the recivers. Different networks might use different email formats. Gateways perform the job of translating email formats from one network to another so that the messages can make their way throw all networks.
Email protocols- if a user wants to sends a message over local  area network across the internet the process is simple but if you went to send a message to a user running a different messaging programme some translations may be necessary. Because of the complexity involved in having many different systems send and receive message in many different formats, email protocols have become necessary. There are following type of protocols used to send and receive e-mail over the network.
1.   X. 400 – the messaging standard with the greatest international impact is called x.400 . it attempts to lay down standard’s for all electronic messaging system in the world. Large scale messaging services such as compuser, America  online use to the x.400 messaging standard. If you send a message to an electronic address over one of these service the service converts the message by using x.400 specification and then send it on to its destinations where it is converted again into the message format the receiving programme uses to make the message understandable to the receiving party.

2.   STMP- STMP stands for Simple Mail Transfer Protocol. It is a TCP/IP protocol that specifies how computer exchange electronic mail. It works with post office protocol (POP) . SMTP is used to upload mail directly from the client to an intimidate host but only computer connected such as Internet Service Provider(ISP) to the internet can use SMTP to receive mail. The ISP server then offload the mail to the user to whom they provide the internet services. STMP is a simple ESCII protocol. After establishing the TCP connection the sending machine operating as the client waits for the receiving machine operating as the server to talk first. The server starts by sending a line of text giving its identity and telling whether or not it is prepared to receive mail. If it is not the client realises the connection and tires again later. If the server is willing to accept email the client ounces whom the email is coming from and whom it is going to. If such a recipients exist at the destination the server gives the client the go ahead to send the message. Then the client the message and the server acknowledge it.   


3.UUCP – UUCP is derived from UNIX to UNIX copy. It is s standard UNIX utility that manages the transmission of information between UNIX system, using serial connection and regular telephone lines. The communication package was developed at Bell Laboratory by Mile Lesk in the mid of 1970’s for serial communication between UNIX systems. It was revised in 1978 .this version became known as Honey Ber UUCP. A newer version known as Taylor UUCP.
UUCP provides the following facilities
1.   File transfer between two host
2.   A communication protocol for email
3.   Control of communication devices
4.   A set of utilities for managing the UUCP project.
4.POP -3-it is a simple protocol used for opening the remote email boxes. This protocol is defined in RFC, 1225 it has the command for the user also. This protocol also defines the method for transfer of email from the remote mail box to the user’s local machine for reading mail later.
5.IMAP -4- IMAP stands for Internet Mail Access Protocol and it is defined in RFC 1064. This protocol is designed to the users who need its use different type of computer for example laptop, workstation etc. This protocol , basically made for the email server that can be access from any machine .inthis protocol the user machine need to access the server. IMAP also have the ability to process the arrived mail form the remote mail server to fetch only. The specified mail .for example using this protocol the user can request send by a particular sender.
6.MIME – MIME stands for Multipurpose Internet Mail Extions. It is widely used internet standard for encoding binary piles to send them as email attachment over the internet. Mime protocol also an email message to contain a non ASCII file such as a video image or a sound and it provides a mechanism to transfer a non text character to text character.
Ø Structure of email message- an email message is made up of binary data usually in the ASCII text format. ASCII is standard that enables any computer, regardless of the system or hardware, to read the text. ASCII code desirable the characters you see on computer screen.
·       There are five section of email message.
1.   Email address
2.   Header
3.   Body
4.   Signature
5.   Attachment

Ø Email addressing system- it is important to understand and follow email addressing scheme for the internet to ensure proper delivery of all outgoing messages.
1.Address syntax- an email address has two parts
                              I.            The domain name of the email server computer on which you have an email account.
                           II.            Your personal identity or account name or user name on that mail server.
·       Note that there are no space allows in email address, email software and server computer will not accept spaces in the email address.
2.Header – the header of the email message is the upper most section. It is displays information regarding the status of the message. A header records message information and provides its to the recipients of the message .Header are present in both outgoing and incoming messages.

3.Body – the body of email message is the primary focus because it conations the actual message.  Although there is no limit to the size of an email message but many ISP do limit the size of an email message.

4.Attachment -email has become all the more attractive to businesses because now it also user to attach a file to any email message any file format such as word process, spread sheet, image or video files can be attach to an email message. Email allow complex data as attachment but not in the body section. Most email application alert you if an incoming message contains an attachment such emails shown an icon within the body of the message to represent an attached file.
5.Signature- the signature for an email message is the personal information which automatically appears at the bottom of the out going message, use of a signature is optional. You can provide any signature information that you wish. The purpose of a signature is to provide a message recipient with personal contact information. By using the signature feature of email software you can avoid typing personal information for each outgoing message

·       Carbon copy – this feature lets you send a copy of the email to another recipient. In this case the main recipient is information about the other people who receive the same message.
·       BCC blind carbon copy in this option the recipient does not known the name of other recipient.

Ø Email content and encoding – RFC 822 specified the headers but left the content entirely up to the users. But on the worldwide internet the approach, his not any more applicable because of the following reason.
1.   Messages may have accent in language
2.   Messages may be in non- letters alphabets
3.   Message may not be using any alphabets
4.   Message may contain the audio, video clipping therefore a solution was proposed in RFC 1521 .This solution call MIME. This type protocol in now widely use.


Ø Email routing – how email is delivered from one system to another over the network is email routing. The IP protocol delivers mail based on the specific email address. This address is expressed at 4 number separated by periods such as 165.52.128.12 . But as it is difficult to remember such complex no. internet addresses are made up of words and letters computers called domain name server DNS translate the alphabetic address into numerical address. So email can be send to the proper location. When you take an internet connection from an ISP then you will be sending your email to the ISP server when it will be using the domain name server to translate the email alphabetic address to the IP address in the numeric address. The domain name server divides the internet into understandable groups or domains. The portion of the domain section is at the for right and of the address for example abe.com is the domain name. Domain name identifies the largest domain name and kind of organization where the persons address resides. The domain name and host name identify the host computers. The domain name and host name identify the email. The receiving host computer looks at the username and delivers the mails to the proper email box. To left of largest domain is specific information about the organization which tells the route to which network email should be send. It can be single –internet address such as ABC or it may be a group of domains and such domain.

 
·       Email encryption – encryption means change the standard code into different code which is understood by the receiver. Encryption protects data when it travels across a cable or telephone line. Using encryption method sender can change the original data in some other code and should give the decode method to receiver.  
·       Address book- the address book offer a convenient place to store useful information for easy retrieval. It also helps you to access internet directory services, so that you can fined people and business on the internet. With the help of address book you have a facility to store email address, phone no, fax no. and digital id’s you can also share address book with other user by creating an identity. 
·       Signature file- signature file is the personal information of the sender which is written at the bottom of the email message. Signature is a message that is optional. If any person writes his signature is a message then the signature of the personal is stored in a file in a binary form called signature file.
·       Email clients- 1
1. Netscape mail client- NETSCAPE message support full featured mail program called NETSCAPE messenger. Netscape messenger is the redefined version of NETSCAPE mails its look like the Microsoft internet
mail. With the help of NETSCAPE messenger you can receive you email and news very quickly and easily. NETSCAPE messenger has a full feature of sending a mail to more than one person at a time. To you use NETSCAPE messenger go to start menu then go to program the NETSCAPE communicator in this you can find NETSCAPE messenger. Writing and sending a message with the help of NETSCAPE and sending is similar to any online service.
2. Outlook Express:  outlook express is the Microsoft email program that is included with window 9x and with internet explorer 4.0 onward .Outlook express puts the word of online communication on your computers desktop. If you want to exchange emails with others than you have to use the different tools of outlook express you can perform the following function with the help of outlook express
1. Manage multiple mails. 
2. Browse messages quickly. 
3. Keep mail on a server.
4. Address book.
5. Send and receive secure messages. 
6. Download news group message for offline reading. 
·       Web based email – each email service’s weather it is an online service, commercial service for it has its own way to      mail.  Most of the email service to someone’s system. The message will travel across the internet to reach its destination. We have given only the addressing of the message properly so that the internet knows
where deliver the message. Here is some web based 3 email accounts such as hotmail.com, rediffmail.com, gmail.com that offer web based email access.

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