What happens when you send an email message? Where does it go, and how does it get to the intended recipient? All this and more coming up next on “Learn Something New Every Day!” [cue theme song]
Email, originally called electronic mail, is a way to send messages between computing machines. It actually started long before the internet ever existed. The “big bang” of email as we know it came in 1971 when the first message was sent between systems on ARPANET (the US government’s computer network for Cold War communication). This was the first time the @symbol appeared to separate the username from the domain or hostname.
Almost 40 years later, email has become the most heavily used communication system on the planet but it hasn’t changed a whole lot. To get an email message from one side of the planet to the other, it needs to get passed through many hands. Let’s take a look at this process as if it was a real letter written on paper.
1. You write your letter, and put it in an envelope. You put on your friend’s address, as well as a return address. We’re all familiar with this part, since we do it every day hour 3 minutes. (technical translation: your email client like Outlook)
2. You have a key in your pocket to unlock a little postbox on your desk. Since you have permission (the key) you can drop your letter in and it falls down a tube into the basement. (username/password to SMTP – Simple Mail Transfer Protocol)
3. The letter falls to a man with a moustache. (why a moustache? It just seems appropriate.) He’s your local postmaster. If you’ve written a letter to somebody in your building, he’ll personally deliver it right away, but chances are it’s going farther than that. A big red postmark is stamped on the envelope. He passes the letter to a very fast munchkin, who has a smaller, pointier moustache for aerodynamic efficiency. Out the door it goes. (the moustachioed man is the MTA – Mail Transfer Agent)
4. The munchkin zips off with your letter in hand trying to find @gmail.com (if that’s where your message was addressed) Obviously these munchkins are females because they stop to ask for directions a lot. They bounce around a few times until they arrive in Mountain View, California and they knock on the door. (this is the process of looking up domain names with DNS records to find the destination IP address)
5. A grumpy man with a moustache (the gmail MTA) answers the door. “Hello, is this gmail.com?,” the munchkin asks. “Does Bob.Robertson live here?”. If the grumpy man says no, the munchkin runs home, and the letter goes in reverse, back to you saying “un-deliverable”. If the grumpy man says “Yes, we have a Bob.Robertson here”, he takes the letter and very carefully scrutinizes that red postmark. He’s grumpy, over-worked, and is looking for any excuse not to take your letter. Some excuses he might give…
“This letter is from Ron Popiel! We don’t want his junk mail here.” (Spam filters)
“This letter is a fake! You aren’t really from @homeoffice.com, you crazy munchkin.” (Sender verification)
“Oh, Bob is in Omaha this week. He asked you to deliver that to him @nebraska-tourism.org” (forwarding)
6. If the letter is accepted, the munchkin runs back home to report a success, and the @gmail.com postmaster waddles back down to the basement to stick the letter in the pile for Bob.Robertson. It’s a mirror image of what happened at the start.
7. Finally (after like 3… maybe 4! minutes) Bob.Robertson checks his mail again. He gets his key out, unlocks his little desktop postbox, and reaches inside to feel for any letters… finding your note!
“Hi Bob! I’m in yur mailbox eating yur cookies. LOLZ! -Jane”
An epic journey taking, perhaps, multiple seconds… but totally worth it.
- A more boring explanation: http://en.wikipedia.org/wiki/E-mail
