The how and what of your e-mail


We send hundreds or e-mails per day, because it’s cheap, it’s fast and most people know how to handle a digital message. Wouldn’t it be nice to understand how this digital courier pidgin works? Well this happens to be my job, explaining you stuff!

So here it is.. 

When we send an e-mail our computer (when using an e-mail client like outlook, thunderbird, windows mail, etc) connects to our e-mail service’s mail server. Which is, if you look at it with a pair of non technical eyes, a big computer which stores all your (and those of others) emails. The server responsible for sending e-mail is called the SMTP, the simple mail transfer protocol, server. One SMTP server can pass on mails to another SMTP server until it finally reaches it’s destination. 

Like a letter, an e-mail has a sender’s address, and a recipient address. When the e-mail you wrote is sent, the e-mail client (again if you are actually using an e-mail client) connects to the SMTP server of the sender’s e-mail service. And then the client transmits the address of the sender, the address of the recipient and of course, not to forget, the content of the e-mail. 

At this point the SMTP server starts working and it tries to find out the whereabouts of the recipient. Using the recipient’s e-mail address, it locates the domain name. And the domain name is everything AFTER the @ sign. @gmail.com = connecting to the gmail domain. 
Each domain has a unique web address called the IP address (which we’ve already came across in earlier posts). The link between all domains and their IP addresses is stored in the domain name registry, this registry is kept in the DNS, the domain name server. When the SMTP server connects to the DNS where the registry is kept, the DNS server sends back the address of the destination SMTP to the sender’s SMTP (it’s hard to read, trust me it was at least equally as hard to write). 

Once all this is done, the SMTP server proceeds to hand over the e-mail to the SMTP server of the recipient. This last SMTP server checks and confirms that the e-mail address is known and hands it over to his best friend, the POP3 Server.

What.. another one? Yes.. I’m afraid so, but bear with me, we are almost there!

The POP3 server or the Post Office Protocol server is a server that has the job to receive mails. Ignore the 3 for now, this is only the version number of the protocol. POP3 servers have e-mail accounts and each e-mail account is mapped to a username and password combination. Once the e-mail has been received by the SMTP server, it’s handed over to the POP3 server which stores the e-mail until the client logs on to pick up his e-mail.

This explains why your computer shouldn’t be on 24/7 in order not to lose e-mails. The data is temporarily stored for you on a remote server. 

Of course this also brings a few problems. As I just explain, the POP server stores the e-mail until you get it. But what if you have a bunch of important unread mails and your computer crashed? Sadly, if you are in fact using POP3, these e-mails are gone forever. To overcome this problem IMAP was introduced, the Internet Access Protocol, this does basically the same as POP with the only difference it keeps a message of the e-mail on the server. As a matter of fact it keeps your local mail client in sync with the server. Delete a mail in outlook, it will be deleted on the server. Delete nothing at all, everything will be kept on the server as well. 

And there you have it, a basic understanding of how e-mail works. Now go on, in the time it took you to read this, you’ve probably received a few dozen e-mails, give that SMTP server of yours some work ;-). 

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