How an Email function?

Answer 1

1 MESSAGE SENDER uses mail software, called a client, to compose a document, possibly including attachments such as tables, photographs or even a voice or video recording. System software, called Transmission Control Protocol (TCP), divides the message into packets and adds information about how each packet should be handled-for instance, in what order packets were transmitted from the sender. Packets are sent to a mail submission server, a computer on the internal network of a company or an internet service provider.

2 INTERNET MAIL ADDRESSES attached to each message are in the form "mailbox@domainname" - one specific example being "webmaster@Google.com." The multipart domain name in the above example denotes a top-level domain (".com") following the second-level domain ("google"). A message is delivered to an individual or a group by the mailbox name ("webmaster").

3 MAIL SUBMISSION SERVER converts the domain name of the recipient's mail address into a numeric Internet Protocol (IP) address. It does this by querying domain name servers interspersed throughout the Internet. For example, the mail submission server can first request from the "root" name server the whereabouts of other servers that store information about ".com" domains (a). It can then interrogate the ".com" name server for the location of the specific "sciam.com" name server (b). A final request to the "sciam.com" name server provides the IP address for the computer that receives the mail for sciam.com, which is then attached to each message packet (c).

4 ROUTERS dispersed throughout the Internet read the IP address on a packet and relay it toward its destination by the most efficient path. (Because of fluctuating traffic over data lines, trying to transmit a packet directly to its destination is not always the fastest way.) The packets of a single message may travel along different routes, shuttling through 10 or so routers before their journey's end.

5 DESTINATION MAIL SERVER places the packets in their original order, according to the instructions contained in each packet, and stores the message in the recipient's mailbox. The recipient's client software can then display the message.