Inam Abidi Amrohvi explains the technology behind sending and receiving email.
The email has to be the single most used internet-based application. In fact most people switch on their computers only to access emails.
As per a Pew Internet and American Life Project survey of 2007, all American adults who use the internet, 92 per cent either send or read an email. That in itself shows the popularity of email. I'm sure the figure would be more or less the same in other countries.
Let's understand the basics of electronic mail.
Email anatomy
The email address basically consists of a user name and a domain name separated by a @ sign, which reads "where it's at".
So for example if my email ID is inam@agrinde.com, 'inam' is my user name and 'agrinde.com' is the domain name.
Agrinde is also the mail server or the computer which has my mailbox. The address ends with '.com' which is the top-level domain. It indicates the type of organisation or the country where the host server is located. In this case, since it is a commercial organisation we use '.com'.
Other top-level domain names include '.ae' for all UAE specific addresses, '.org' for non-commercial organisations, '.net' for organisations into networks such as the ISPs (Internet Search Providers), and '.edu' for educational establishments.
How it travels
Just like postal mail, electronic mail has a sender, a recipient, and a message to send. The role of the postman is taken over by a client and a server computer, and the physical path transforms into a digital domain called the internet. The email client is the software that we use to compose our emails. Microsoft Outlook, Outlook Express, Eudora, and Thunderbird are some of the popular email clients used.
Once we click on the send email option, the client starts to connect with the SMTP server. Simple Mail Transfer Protocol or SMTP is the standard protocol (a protocol is a set of rules that computers use to communicate with each other) used to send messages on the internet. It works in conjunction with the Post Office Protocol (POP) server, which is often used to receive messages.
When the connection is established between the client and the server, the client sends the message. The server then establishes the identity of the receiver and delivers the message to the mail server of the recipient. The recipient's mail server then delivers the message when the client connects to it the next time and requests for retrieval. All this happens in a few seconds!
Why does email bounce?
I'm sure most of us have had one or more emails bounce back into our inboxes. This happens for to several reasons. The first and most common reason is because the recipient's mailbox is full and cannot accept any new mails.
It could also be because the domain name doesn't exist, or the user name is spelt incorrectly or is non-existent. These all fall under the category of soft bounce because the email in this case is initially accepted by the recipient's email server only to be returned to the sender after verification.
The second is hard bounce. In this case the email is returned to the sender without being accepted by the recipient's mail server. This happens if the email server is advised to block certain addresses (could be an anti-spam filter) or is too busy to handle the request.
Sometimes the email just bounces back due to a network failure at the recipient's end.
I hope now that the next time you send an email to a friend or family, you'll appreciate the technology that transmits your message in a matter of seconds.
- Disclaimer: The opinions and ideas expressed here are purely those of the author and in no way reflect the views of Notes on any technology.
— The writer is a guru of tech who runs a trading company in Dubai.
