Page 266 - DCAP312_WEB_TECHNOLOGIES_II

Web Technologies-II

Notes 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.
Internet Mail Addresses: Attached to each message are in the form “mailbox@domainname”
– one specific example being “webmaster@seniorindian.com.” The multipart domain name in
the above example denotes a top-level domain ( “.com”) following the second-level domain
( “seniorindian”). A message is delivered to an individual or a group by the mailbox name
( “webmaster”).
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 where about of other servers that store information about “.com” domains. It
can then interrogate the “.com” name server for the location of the specific “sciam.com” name
server. 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.

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.
13.3.3 Advantages of E-mail

• E-mails are easy to use. You can organize your daily correspondence, send and receive
electronic messages and save them on computers.
• E-mails are fast. They are delivered at once around the world. No other form of written
communication is as fast as an email.

• The language used in emails is simple and informal.
• When you reply to an email you can attach the original message so that when you answer
the recipient knows what you are talking about. This is important if you get hundreds of
emails a day.

• It is possible to send automated emails with a certain text. In such a way it is possible to
tell the sender that you are on vacation. These emails are called auto responders.
• E-mails do not use paper. They are environment friendly and save a lot of trees from
being cut down.
• E-mails can also have pictures in them. You can send birthday cards or newsletters as
emails.
• Products can be advertised with emails. Companies can reach a lot of people and inform
them in a short time.
13.3.4 Disadvantages of E-mails

• E-mails may carry viruses. These are small programs that harm your computer system.
They can read out your e-mail address book and send themselves to a number of people
around the world.
• Many people send unwanted emails to others. These are called spam mails. It takes a lot
of time to filter out the unwanted emails from those that are really important.

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