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How Email Works

This presentation depicts how the functioning of emails get unnoticed in our lives. It contains the brief overview of various things related to protocols and servers in the electronic mail's context.

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How Email Works

  1. 1. Text How Electronic Mail Works The Protocol cog-wheels of the Virtual World Sahil Babbar, Neeraj Vaishnao
  2. 2. Introduction Over “204 million” emails are sent per minute! Indispensable in the 21st Century. Robustness & Secureness Protocols Involved Mail Server-Client Interaction
  3. 3. Beginning the Magic User is provided with an editor to type the message(for web-based email client or desktop-based client). Connection is established between Client and SMTP server over the TCP. TCP Handshake follows. First the client sends a request to the server who is waiting for the client to join, then server responds back with ACK, and then in the third transmission (from the client to the server).
  4. 4. Click “Send” When the user clicks the send button then the email is transmitted to the SMTP server called Outgoing SMTP Server. The message along with some headers added from Transport Layer is send to the Network Layer in the form of Datagrams. Then this message is sent to SMTP server of the ISP. Note: Reliable delivery of this message is ensured by the SMTP protocol and not by the Network Layer.
  5. 5. On the Way - Part I Message needs to be reliably transmitted over the non- reliable network. SMTP Packet carries: Sender’s Address, Receipt’s Address, Subject, Message, Checksum. Parity check is done to ensure the data consistency over the unreliable network. TCP: Reliable Delivery, Error Control, Congestion Control
  6. 6. On the Way - Part II The Outgoing SMTP server sends the SMTP packets to the SMTP Server of the ISP of Receiver(called Destination SMTP Server). The Destination SMTP Server gets the information about the Outgoing SMTP Server, transmitting message according to MX(Mail eXchange) Record stored in DNS Server (Domain Name System) of the network over SMTP.
  7. 7. Reaching the Receiver This is done by obtaining the MX (Mail Exchange) Record associated with receiver’s email address. Example: If the receiver’s address is having the domain name as, the MX Record travel in the following manner: Root Server -> DNS Server -> Google’s DNS Server -> IIITD’s SMTP Server
  8. 8. 1) Importance of Email in everyday corporate/govt/ personal life .  2) Hence it is important to    
  9. 9. Click “View” •Emails can be sent and viewed in various ways and one of them is using desktop email applications. •Desktop application maintains a connection with a remote server called MTA (Mail Transfer Agent) for storing the emails. •The user’s inbox is linked to MDA (Mail Delivery Agent) which is responsible for addition of new emails to user’s inbox. In Unix environments, the default settings for storing emails locally is present, which stores them in the HOME directory of the user. When users start their email clients then all the emails stored in the directory are shown and therefore, the remote server goes out of the picture.
  10. 10. Post Office Protocol v3 Its Storage in SMTP till the mail client on client’s machine does not request for an update. However, the mail is not transferred to the receiver’s machine immediately, it is stored in the SMTP server itself and gets transferred to receiver’s machine only after the receiver opens his email box and queries the mail server to retrieve the new emails. When the receiver initiates to access the email, another protocol called POP3 (Post Office Protocol) gets activated and fetches the mail updates onto the receiver’s machine.
  11. 11. Internet Message Access Protocol v4 •The main difference between both POP3 and IMAP is that POP3 stores the email messages, locally in the user’s machine and deletes the message from the server, once it is downloaded to the client’s machine and IMAP allows the user to remotely read the emails on the remote mail server and temporarily stores them locally. •IMAP serves as a cloud storage option. •Both POP3 and IMAP4 are used for receiving emails and SMTP and MSA are used to send emails. There are various email catching softwares available online which directly queries the Destination SMTP Server and display the emails in a browser window, although, these software run on localhost configurations.
  12. 12. Crux
  13. 13. Summary The concept of electronic mail has been a breakthrough in the history of communication and people have become so used to it that they often ignore the functioning engines behind their screens.