I get lots of email, some of it I want, some of it I’d rather not see. I’m sure that’s true for everyone with an email address. If I get the email, how does it get there? If I send email to my brother, how does my computer know how to get the email to him? It’s a bit of a complicated process, so we’re going to break it down and start by talking about Email and DNS.

One day, I decide I want to send an email to myfriend@example.com.

Why did I say example.com rather than a domain like gmail.com or hotmail.com? That’s because example.com is a domain that was set aside at the beginning of Internet time so people can use it in examples without referring to existing domains. It’s an example, just like its name.  It’s useful to use it because existing domains have been known to go away or change behavior, but example.com is always that, an example.

Ok, back to the subject at hand!

I’m sending email to myfriend@example.com and my first question is how does my email know where to send it?  My second question is, do I send it to example.com or somewhere else?

The geniuses that set up the Internet originally knew that the owner of a domain wasn’t necessarily the same person that ran the domain. The  domain computerlamp.net is what has this blog and while I own that domain, I don’t run things around here. I let DreamHost (Hi guys!) run this for me. That means that they handle my email, I don’t. All I do is read it.

DNS lets us know this by using the MX record. (MX means ‘mail exchanger’. They skipped the E when they made the acronym.)

The MX record for computerlamp.net is:

computerlamp.net mail is handled by 0 mx2.sub4.homie.mail.dreamhost.com.
computerlamp.net mail is handled by 0 mx1.sub4.homie.mail.dreamhost.com.

I did this using the command host.  Using the -t flag, my command was:

Alpha:~ computerlamp$ host -t MX computerlamp.net

If I wanted to know who handles the email for gmail.com, I’d do:

Alpha:~ computerlamp$ host -t MX gmail.com
gmail.com mail is handled by 40 alt4.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 20 alt2.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 30 alt3.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 10 alt1.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 5 gmail-smtp-in.l.google.com.

I got 5 responses back… with numbers in them! Next time, we’ll talk about what those numbers mean.