What Is an Email Address?

By Nacie Carson

An email address is an Internet identifier used to direct and route email messages. Like street addresses, email addresses are used to define where and to whom an email message can be delivered. Email addresses are sent across the Internet using the Simple Mail Transfer Protocol (SMTP), and typically conform to the naming convention of username@domain.com. The domain refers to the host website, while the username indicates which user specifically in that domain will receive the message.


Messages directed to an email address can be retrieved from the email mailbox, the Internet-based or software program where messages are stored. Mailboxes may be used on or offline.

Invalid Addresses

Messages sent to an email address that doesn't exist will be returned to the sender email address with a note of failed delivery.

Naming Conventions

The username of an email address may have up to 64 characters, and may consist of upper and lowercase letters, numbers and certain types of punctuation.

Free Email Addresses

Many websites, such as Google, Yahoo, MSN and Hotmail, offer free email addresses to registered users.

Email Address Internationalization

There is an Internet Engineering Task Force called Email Address Internationalization that is working to solve several key issues that prevent email from being a universal form of communication due to restrictions in naming conventions.