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  1. 1. Shashwat Shriparv InfinitySoft
  2. 2. INTRODUCTION In the early days of ARPANET, email is consisted exclusively of text messages written in English and expressed in ASCII. For this environment , RFC 822 did the job completely. Nowadays, on the worldwide Internet, this approach is no longer adequate.
  3. 3. The problems include sending and receiving are 1. Message in language with accents (eg: French and German). 2. Message in nonLatin alphabets( eg: Hebrew and Russian) 3. Message in language without alphebets(eg: Chinese and Japanese) 4. Massage not containing text at all(eg: audio and video
  4. 4. MIME-Multipurpose Internet Mail Extensions • A solution was proposed in RFC 1341 and updated in RFC 1521.This solution called MIME is now widely used. • The basic idea of MIME is to continue to use the RFC 822 format, but to add structure to the message body and define encoding rules for non-ASCII messages. • BY not deviating from 822, MIME massage can be sent using the existing mail programs and protocols . • All that has to be changed are the sending and receiving programs, which users can do for themselves
  5. 5. • MIME defines five new message headers They are Header Meaning MIME-Version: Identifies the MIME version Content Description: Human-Readable string telling what is in the message Content-Id: Unique identifier Content-Transfer-Encoding How the body is wrapped for transmission Content-Type: Nature of the message
  6. 6. Type Subtype Description Text Plain Rich text Unformatted text Text including simple formatting commands Image Gif Jpeg Still picture in GIF format Still picture in JPEG format Audio Video Basic Mpeg Audible sound Application Octet-stream Postscript An un interpreted byte sequence A printable document in PostScript Message Rfc822 A MIME RFC 822 message Partial Message has been split for transmission External Body Message itself must be fetched over the net Multipart Mixed Alternative Parallel Digest Same message in different formats Parts must be viewed simultaneously Each part is a complete RFC 822message Movie in Mpeg format Independent parts in the specified order
  7. 7. Message Transfer • The message transfer system is concerned with relaying ,messages from originator to the recipient. • Establish a transport connection from the source machine to the destination machine. • There are situations in which this does not work. • To overcome this we can do is ….
  8. 8. SMTP-Simple Mail Transfer Protocol • Within the Internet email is delivered by having the source machine establish a TCP connection to port 25 of the destination machine • Listening to this port is an email daemon that speaks SMTP . • SMTP is a simple ASCII protocol. • If the server is willing to accept mail, the client announces whom the email is coming from and whom it is going to.
  9. 9. Email Gateways • Email using SMTP works best when both the sender and the receiver are on the Internet and can support TCP connection between sender and receiver. However, many machines that are not on the Internet still want to send and receive email from Internet sites.
  10. 10. Final Delivery • A simple protocol used for fetching email from a remote mailbox is POP3(Post Office Protocol) which is defined in RFC 1225. • A more sophisticated delivery protocol is IMAP(Interactive Mail Access Protocol) which is defined in RFC 1064. • The third delivery protocol is DMSP(Distributed Mail System Protocol), which is part of the PCMAIL system and described in RFC 1056.
  11. 11. • Independent of whether email is delivered directly to the workstations or to a remote server, many systems provide hooks for additional processing of incoming email. • An especially valuable tool for many email users is the ability to set up filters. • These are rules that are checked when email comes in or when the user agent is started. Each rule specifies a condition and an action.
  12. 12. • Another delivery feature often provided is the ability to forward incoming email to a different address. This address can even be a computer operated by a commercial paging service. • Ability to install a vacation daemon.
  13. 13. Email Privacy • When an email message is sent between two distant sites, it will generally transit dozens of machines on the way.Any of these can read and record the message for future use. • Widely used secure email systems are. PGP PGM
  14. 14. Shashwat Shriparv InfinitySoft