Reader and subscriber Jack Carmena wrote recently to ask about domain names and email addresses. I realized that, although I had written about domain names before, a more basic explanation and their relationship to email addresses and Internet computers could be important for many other readers.
Thank goodness that Jack asked…
Why do some email addresses end in “.com” and some in “.net’?
What dictates that?
Thanks for the question, Jack. Now I have an article
The email addresses are a function of the domain name of the ISP the emailer is using or, perhaps, of the domain name registration they have purchased (such as my terryscomputertips.com).
.com and .net are two examples of the portion of the domain name that is called the “high level domain.”
There are a number of high level domains. The most common, for U.S. users of the Internet, are .com, .net and .org. There are also .gov and .mil that are U.S.-specific.
Originally, .com were restricted to commercial entities, .net restricted to entities providing networking services, .org restricted to non-profit organizations, .edu to accredited educational organizations, .mil to U.S. military and .gov to U.S. government. The last three, .edu, .mil and .gov, are still restricted in this way. Anyone, even people not in the U.S., can now register .com, .net and .org addresses.
Countries, including the U.S., also have a country-specific high level domain. Most of the time, the two-letter abbreviations are the ones you would expect for the country’s name — in their language. Here are a few examples:
.us = U.S.A.
.uk = United Kingdom
.de = Germany
.fr = France
.es = Spain
Outside the US, 3-level domains are common for email — they still like to keep the .com designation, although some abbreviate it .co. In the U.K., for example, you might have an email address that ended @googlemail.co.uk.
On the other hand, sometimes the country names conflict when they are abbreviated, so we end up with some weird high-level domains, too. Examples are:
.is = Iceland
.il = Israel
You can see the full list of country codes for internet domains at the Internet Assigned Number Authority.
I have several domains, including:
- TheNextWindow.com (my general blog)
- Terry’s Computer Tips blog
- PC Repair Site.info
- XP Repair Site
- Drawing on the Web, my web design blog, and
- Windows Vista Repair Site
Notice how TerrysHomeTheater.com simply drops the visitor to a specific page (the beginning of my Terry’s Home Theater section). Depending on which domain registrar I use (I use GoDaddy.com), you can set it to do just like this or you can even create "framed pages" where your desired URL shows in the browser’s address bar. Or, you can do like I’ve done, where this is in my web-hosting account, and acts as if it were completely independent of my other domains.
Now, what does the “www” mean? The third-level of the domain name specifies a particular computer in the domain. “www.” is the accepted standard for the web server, although many web servers also answer to the domain name without the “www.”
Other web servers, if the web designer wishes, may answer to other values in this third-level of the domain name. This position is called the “subdomain.” Subdomains often use the same server, but that’s not required. The web master (if he/she has access to the DNS records for their domain) can set the DNS of a subdomain to point to any IP address that they wish.
In other words, the “fully quallified domain name” (abbreviated FQDN) is:
My computer tips blog is an example of a subdomain. My Terry’s Computer Tips Blog is found at http://blog.terryscomputertips.com. My blog.terryscomputertips.com subdomain is actually running on the same computer as www.terryscomputertips.com .
Another example is the webmail server for Cox.net — http://webmail.cox.net .
So, you may see email addresses that have any domain name, whether it has 2 parts, 3 parts, 4 parts, etc.