Email is so commonly used in business, education and personal life that it's easy to take it for granted and not think about just how your messages get where they're supposed to go. Every email address is unique and made up of three parts designed to tell the Internet how to route the mail so that it reaches your inbox.
The first part of an email address is the user name, which identifies you personally on the mail server that you use. Each user name on a server must be different and consists of letters, numbers or special characters such as underscores or periods. Your user name might be your first initial and last name, a business name or anything else you want to use to identify yourself on the Internet.
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The symbol "@", called the "at" symbol, connects the user name of an email address to the mail server, or domain. It tells the Internet that your user name can be found at that domain.
The domain name in an email address appears after the @ symbol and identifies the Internet domain that handles your email. It can be further broken down into two parts: the name of the computer or server that handles the mail and the top-level domain, often "com," "gov" or "edu," which stand for commercial business, government agency and educational institution, respectively, according to St. Edward's University. An example of a domain name is "ehow.com."