Email transfer part 1


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  • Email transfer part 1

    1. 1. Sub Topic : E-Mail transfer (Part 1) 1
    2. 2. Recap• In the previous class, you have learnt about – DNS server and its functions 2
    3. 3. Objectives • On the completion of this period, you would be able to Understand about – What is e-mail ? – The advantages of e-mail – E-mail Components – E-mail Functions – E-mail transfer mechanism 3
    4. 4. Introduction to E-mail (Electronic mail)Fig.1 4
    5. 5. What is Email?• E-mail is one of the most popular services available through the Internet. It is similar to a mail, but is sent electronically across the Internet. Telephone E-mail Post Speed High Moderate Low Synchronized Yes No No Formality Varies Moderate Varies Conferencing Small Group Any to all One-way only Security Moderate Low High 5
    6. 6. Letter Analogy• Write a 20-page letter to Grandma• Number the pages• Put each page in a separate envelope• Drop them in the mail 6
    7. 7. Letter Analogy Continued• Do letters take the same route• Do letters arrive at the same time• Do letters arrive in any particular order• How does Grandma handle multiple letters arriving• What if a letter gets lost• Intermediate Post Offices act like routers• Mail boxes are similar to “ports” 7
    8. 8. Electronic Mail• Electronic mail shortly known as e-mail was created to allow two individuals to communicate using computers• It is an electronic way of communicating information from one computer to the other which are connected through network• E-mail has emerged as inexpensive and efficient means of communication 8
    9. 9. E-MAIL Features• The present e-mail system offers the following features – Composing and sending a message – Sending a single message to many persons – Attaching Graphics, Voice, Video to message – Storing, Forwarding, Deleting, Replying to a received message 9
    10. 10. E-mail Technology• E-mail systems carry and manipulate e-mail messages: – E-mail servers. – Based on store-and-forward technology.• Three types of e-mail systems widely used today: – POP (Post Office Protocol). – IMAP (Internet Message Access Protocol). – Web-based e-mail. 10
    11. 11. E-mail Technology• Web-based e-mail accounts allow you to use a browser to access your e-mail messages Fig.2 11
    12. 12. E-mail Technology• A POP server is a computer that stores your incoming messages until they can be transferred to your hard disk – E-mail client software – SMTP server Fig.3 12
    13. 13. E-mail Functions• From the user point of view, e-mail perform the following functions – Composition (providing text editor features) – Transfer (message from sender to receiver) – Reporting (delivery reports) – Displaying (incoming and sent mails) – Disposition (forwarding, archiving, deleting) 13
    14. 14. E-Mail Overview• Any person with an e-mail account can send and receive e-mail messages Fig.4 14
    15. 15. E-Mail Overview• Basic e-mail activities – Writing – Reading – Replying – Forwarding Fig.5 15
    16. 16. How is e-mail Transferred ?Heres what happens to an email when it is transferred overthe Internet 1. It is broken up into a whole lot of same-sized pieces (packets) 2. A header is added to each packet that explains where it came from, where it is going and how it fits with the rest of the packets 3. Each packet is sent from computer to computer until it finds its way to its destination 16
    17. 17. E-mail Transfer (Contd.,)4 Each computer along the way decides where next to send the packet. This could depend on things like how busy the other computers are when the packet was received. The packets may or may not all take the same route5. At the destination, the packets are examined. If there are any packets missing or damaged, a message is sent asking for those packets to be resent. This continues until all the packets have been received intact6. The packets are reassembled into their original form 17
    18. 18. How does Email Work?Fig.6 18
    19. 19. Transfer of Email (detailed procedure)• Analogy to postal delivary system – Letter : Mail User Agent – Postal Address : Email address – Postman : Mail Delivery Agent – Post Box : Mailbox / Maildir – Post Office : Mail Transfer Agent 19
    20. 20. Important Terms• Mail User Agent (MUA) – Interface used for users to send and receive mail – Translates pop/imap commands for user – E.g. rediffmail, yahoomail, gmail (web based) outlook, eudora – Allows users to retrieve and compose emails• Mail Delivery Agent (MDA) – Delivers email from MTA and distributes to individual mailboxes – E.g. POP server 20
    21. 21. Important Terms• Mail Transfer Agent (MTA) – Transfers email between machines using SMTP – Sends mail to destination – Performs SMTP functions – E.g. SMTP Server• Mailbox – Stores users mail 21
    22. 22. Illustration of Email Transfer 22
    23. 23. Email Transfer - Step 1• Sender creates and sends an email – The originating sender creates an email in their Mail User Agent (MUA) and clicks Send – The MUA is the application the originating sender uses to compose and read email, such as yahoomail, gmail, Eudora, Outlook, etc 23
    24. 24. Email Transfer - Step 2• Senders MDA/MTA routes the email• The senders MUA transfers the email to a local Mail Transfer Agent (MTA) (SMTP server)• The MTA accepts the email, then routes it to local mailboxes or forwards it if it isnt locally addressed 24
    25. 25. Email Transfer - Step 3• MTA to MTA Transfer (Sender’s SMTP Server to Receiver’s SMTP Server)– To find the recipients IP address, the MTA contacts the Domain Name System (DNS)– When transferring an email, the sending MTA handles all aspects of mail delivery until the message has been either accepted or rejected by the receiving MTA– The email enters the Internet network cloud, where it is routed to the receiver’s MTA along a chain of routers 25
    26. 26. Email Transfer - Step 4• Firewalls, Spam and Virus Filters– Before reaching the receiver’s MTA an email may be transferred to at least one firewall– An email encountering a firewall may be tested by spam and virus filters before it is allowed to pass inside the firewall– These filters test to see if the message qualifies as spam or malware. If the message contains malware, the file is usually quarantined and the sender is notified– If the message is identified as spam, it will probably be deleted without notifying the sender 26
    27. 27. Email Transfer -Step 5• Delivery– The email makes it past the hazards of the spam, and is accepted for delivery by the receivers MTA– The MTA calls a local MDA (POP Server) to deliver the mail to the correct mailbox, where it will sit until it is retrieved by the recipients MUA 27
    28. 28. Summary In this class, you have learnt about• E-mail is an electronic way of sending mails• E-mail contains header , greeting , text and signature• E- mail address contains username , @ and domain name• Non text information can also be transmitted through e-mail using MIME attachments 28
    29. 29. Quiz1) ____is a storage area to store e-mailsA) Mail Box2) In e-mail id, the prefix refers to the ___A) User Name3) Which symbol is used to connect the user name to the domain name portion ?A) @ 29
    30. 30. Quiz4) ____allows non-text data to be sent along with an e- mail messageA) MIME5) What type of files have .wav extension?A) Audio Files (Microsoft)6) Expand .mpeg used as extension for image filesA) Moving Picture Expert Group 30
    31. 31. Frequently Asked Questions1. Explain how e-mail is transferred2. Explain the components of E-mail3. What are the advantages and disadvantages of E-mail ? home 31