Understanding E-mail Addresses

E-mail addresses typically have two main parts: the user name and the domain name.

Here's an example: professor@learnthenet.com

professor is the user name and refers to the recipient's mailbox. After the @ sign comes learnthenet, the host name, also called the domain name. This refers to the mail server, the computer where the recipient has an electronic mailbox. It's usually the name of a company or organization.

The end of the domain name consists of a dot (".") followed by three or more letters (such as .com and .gov) that indicate the top-level domain (TLD). This part of the domain name indicates the type of organization or the country where the host server is located.

Here are the most common top-level domains currently in use:

.aero--For the air-transport industry

.biz--Reserved for businesses

.com--For businesses and commercial enterprises; most companies use this extension.

.coop--Reserved for cooperatives

.edu--For educational institutions and universities

.gov--Reserved for United States government agencies

.info--For informational sites

.int--For organizations established by international treaties

.jobs--For employment-related sites

.mil--For the United States military

.mobi--For sites related to mobile devices

.museum--For use by museums

.name--For use by individuals

.net--For networks; usually reserved for organizations such as Internet service providers

.org--For non-commercial organizations

.pro--For use by licensed professionals, such as attorneys and physicians

.tel--For services connecting phone networks and the Internet

.travel--For travel-related services, like airlines, hotels and agents

More information about top-level domains is available at the website of ICANN, the organization that administers TLDs.

For e-mail addresses outside of the United States, there is often a two letter country code. For instance, .ca indicates Canada, .uk indicates the United Kingdom and .mx indicates Mexico. Here's a complete list of Internet country and territory codes.

Below you can see the difference between an e-mail address and the address of a website, also known as a URL. Notice that a Web address never contains an "@ " sign.

E-mail address: president@whitehouse.gov

Web address: www.whitehouse.gov

For a fascinating history of the now ubiquitous @ sign, read "Where It's At."

Last update: Jan 11, 2010