Parts of an Email Address and the Characters You Can Use in Them

Learn which characters you can use

At symbol traced in sand, close-up
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Email addresses — for example, "me@example.com" — encompass several elements. Most prominently, you find the @'character in the middle of every email address. After that comes the domain name, which is "example.com" in our example.

The Domain Name

Domains on the Internet follow a hierarchical system. A certain number of top-level domains ("com," "org," "info," "de," and other country codes, for example) exist, and these make up the last part of every domain name. Within each top-level domain, custom domain names are assigned to people and organizations applying for them. The domain owner can then set up sub-level domains freely, to form something like "bob.example.com."

Unless you buy your own domain, you don't have much say over the domain name part of your email address — meaning, if you are creating a Gmail address, you have no choice but to use "gmail.com" as the domain name.

The User Name

Preceding the @ sign is the username. It designates who at a domain is the owner of an email address — in our example, "me."

Whoever set up your email address (you, your school, your employer, etc.) can select the username freely. When you sign up for a free email account, for example, you can enter your own creative username.

There are some limitations, however — for example, the number of characters in the email address and the allowable characters. Everything that is not allowed explicitly is forbidden.

Characters Allowed in Email Addresses

The relevant Internet standard document, RFC 2822, lays out which characters you can use in your new email address.

In the standard's parlance, the username in an email consists of words, separated by dots. A word in an email address is called an atom or quoted string. An atom is a sequence of ASCII characters from 33 to 126, with 0 to 31 and 127 being control characters, and 32, whitespace. A quoted string begins and ends with a quotation character ("). In between the quotes, you can put any ASCII character from 0 to 177 excluding the quote itself and the carriage return. You can quote the quote with a backslash to include it. The backslash will quote any character. The backslash causes the following character to lose the special meaning it usually would have in the context.

If this sounds complicated, don't worry: It all boils down to a few simple, easily understandable guidelines, In short, you can use any ASCII alphanumeric character in your email address, as well as any characters between ASCII 33 and 47. These include, for example:

  • !
  • #
  • $
  • %
  • &
  • -
  • ~

In short, you can use lower-case characters, numbers, and the underscore to create your email address.