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Anatomy of an Email Address

Michael Coghlan on Flickr

If you have an email address, likely you barely notice how an address works. For example, can you use odd characters like a period or underscore or asterisk in an email address?

Email addresses have two parts separated by the @ (called ‘at’) symbol, a local-part and a domain, as in . jane.doe is the local part and anytown.com is the domain. Mail servers are software that use the domain to find the server that handles your email. Once your email arrives at your email server, the local part is used to deliver email to your mailbox.

More interesting, are the rules around email addresses. The local part can be up to 64 characters while the domain part can be up to 255 characters. And there’s only one @ symbol allowed, between the local and domain parts.

The local part can be uppercase and lowercase Latin letters, A to Z and a to z, as well as digits 0 to 9, special characters !#$%&’*+-/=?^_`{|}~, and a dot or period in some cases. jane.. is not allowed but ‘jane..doe’@anytown.com works.

The domain part has stricter rules. Only letters, digits, and hyphens are allowed.

What actually works, however, depends on your mail server. Probably it’s a good idea not to get too crazy or fancy the next time you create an email address!

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