What exactly is an email and how does it travel through the Internet?
I’ve testified about this numerous times, and I am sharing here how I explain it when I testify in court. When providing testimony to judges, juries and even lawyers, they want to have non-technical explanations that use plain language. I like to think that I am pretty good at that, and especially coming up with good simple analogies that everyone is familiar with. First you have to look at what an email is with its basic definition. “Email” stands for “electronic mail”, so it helps to compare it to regular mail using the good old fashion postal service. Let’s dig in on the journey of an email! (I’ve also included at the end how text messages travel from user A to user B in a similar manner).
Let’s compare an email to regular mail
First, there is a message which you place in an envelope. Second, there is a sender name and address and a recipient name and address. Let’s call them Bob and Tim. Bob wants to send a letter to Tim. He writes a message and places it in an envelope with his address as the sender and Tim’s address as the recipient. He drops the envelope in a mailbox. Now, does the envelope go directly to Tim’s address? No, it does not. The envelope has to go through the Postal Service which will redirect the envelope. For email, your Email Service Provider is like the post office. When Bob sends a letter to Tim, it first goes to the post office who sorts it, and then sends it to Tim. If Tim is in a different country, the post office in Bob’s country would send it to the post office in Tim’s country. Then, in the other country, they will send it to Tim’s address. Simple enough, yes?
The journey of an email
When you’re writing an email you type your message, pick a receiver and subject. The message is placed in a container by your email program which is similar to an envelope. Let’s assume that Bob has a Gmail account and Tim has a Hotmail account. The email service is like a post office and different services is kind of like being in different countries. Bob writes an email message from his Gmail account and sends it to Tim’s Hotmail account. The email does not go directly to Tim, just like a letter does not go directly to an individual. It must travel through “servers” which are like post offices. People sometimes don’t want to admit they do not know what a server is and are afraid to ask. A server is simply a computer somewhere. Therefore, a Gmail server is a computer that Google owns, and a Hotmail server is a computer that Microsoft owns. Still with me? Good.
When Bob sends an email, it first goes to a Gmail server because he has a Gmail account. When the Gmail server receives the email, it puts some information on it called a “header”. An email can have multiple entries in the header if it travels through multiple servers. This is like the ink stamp that the post office places on the envelope and over the stamp. Some of you may have never mailed an actual letter but trust me on this! LOL. When the Gmail server receives the email message for Tim, it says “oh, this needs to go to Hotmail”. The Gmail server then sends Bob’s email to a Hotmail server. When the Hotmail server receives the email, it looks at the address, adds information to the header, and then sends it to Tim’s email account. Voilà!
Actually, that’s not quite how it ends
The Hotmail server will hold the email until Tim fetches it. In fact, the sever will keep a copy until the email is deleted. This is one difference with paper letters. The post office does not, or should not, keep a copy of your letters. There are times when it does happen. When I was with the drug section, we intercepted packages all the time. But that’s another story. Email servers do keep copies of emails and this allows users to see or “download” their emails from multiple devices.
What about mobile text messages?
Mobile text messages are very similar except that your “post office” is your telephone’s cellular data provider. In Canada we have Telus, as an example, and in the US, they have Verizon. When Bob sends a text message to Tim and Bob is with Telus and Tim is with Verizon, they are using their cellular data to send messages back and forth. Again, the messages do not go straight to the other user. First, Bob’s message goes to a Telus server which is just a computer owned by Telus. Telus receives the text message and sees that the recipient is a Verizon phone number. Therefore Telus sends the message to a Verizon server. When Verizon receives it, it sees that the phone number is Tim’s account and sends the message to Tim’s mobile device.
What about WiFi messages and Apple iMessage?
Text messages are a little bit different than email because mobile devices can use cellular services or WiFi. The way I described WiFi messages and Apple iMessages is by using a courier analogy. By courier, I mean services like Purolator, UPS, or FedEx. Apple for instance has a service called iMessage. This service only works with other apple devices. You cannot send an iMessage from an iPhone to an Android phone for example. Basically the same service provider (Apple) receives and delivers the message. So if both Bob and Tim have iPhones, they can send each other iMessages only on WiFi and do not even need a cellular data provider. They in effect, “bypasses” the good old fashioned post office. Just like a Courier service receives and delivers a package, Apple handles all of the message transmission.
Conclusion
Using real-world and “common” analogies, like the post office and courier service, is very helpful in explaining technology to lay-persons. It avoids the use of technical terms and keeps things as simple as possible. It can be used to explain many other things. For example, email spoofing is when an attacker uses someone’s email address to send a malicious messages. This is like changing the sender email address on the envelope. Therefore never trust the contents inside the envelope. Just because you recognize the sender address does not meant they actually sent it!
If you have any questions, contact me on LinkedIn. It is the best place to reach me.
https://www.linkedin.com/in/alain-filotto