DNS, BIND, MX records and Email

BIND, or DNS (Domain Name System) is kind of like the glue that makes email work. Have you ever sent an email and wondered 'how does it know where to go?' As a general discussion, computers prefer to think in terms of numbers. Ever computer on the internet has an IP address - a quad  of dot separated numbers, ranging from 0 to 255. But this doesn't work to well for humans.

Lets say you want to tell someone about this website, spam-dam.com. You probably wouldn't bother if you had to tell someone to point there browser at the IP address for spam-dam.com - 66.249.10.153. DNS is what glues the name spam-dam.com to the IP address 66.249.10.153. Because of DNS, you can mention spam-dam.com to anyone, and their browser will be able to find and load this website.

When you type the name spam-dam.com into your browser, the browser will look-up the IP address for spam-dam.com, and then request the home page from the web server at 66.249.10.153. This look-up is done using the DNS servers specified in your network configuration setup. Without DNS,

Anyone who owns a domain name has the rights to park his DNS anywhere he likes. Typically parked with either the domain name registrar, the ISP, or the web hosting company. In this situation, the domain name owner has little ability to modify DNS records, and must rely on someone else to make changes for them. This is perhaps, as it should be, since changes made to DNS can render a website unavailable if not done correctly.

But with a little thorough understanding, anyone can take control of their DNS and have it hosted at one of the free/low-cost domain name parking services such as zoneedit.com, dyndns.org or easydns.com. The advantage to doing this, is that you are free to add, edit, and delete your DNS records, any time you want. You can even create sub-domains until the proverbial cows come home.

When discussing DNS for an email server, things are slightly more complicated than outlined here for resolving a web address. There's actually two DNS records needed in order for an email to figure out where it needs to go. Or more accurately, the server needs to figure out where to send the email. The pages in this section discuss this in detail. Don't worry, it's really not difficult to get your arms around this stuff, and understanding DNS is going to be important if you are running a mail server. We'll start with MX and A records on the next page.

BIND is another name for DNS, and refers to the original DNS server named BIND on Linux and Unix platforms.

A website at dnsreport.com is indispensable to anyone running a mail server or diagnosing problems with any aspect of DNS setup. You can perform MX record lookups and many other things. Give it a look over and you'll quickly see how handy it is to know about.