What is the syntax of an email address (local-part@domain)?

An email address has two parts separated by the at sign. The local part appears before the at sign and the domain appears after it. The local part is the mailbox name on the server and the domain is the host that receives and routes the message. For example, in captain@tidalmail.com, captain is the local part and tidalmail.com is the domain.

Behind the scenes, the domain must exist in DNS and must publish valid MX records or the address cannot receive mail. This entire structure was formalized in RFC 5322.

A final piece of history adds depth to this story. The at sign was chosen in 1971 by Ray Tomlinson when he sent the first networked email. He chose it because it was already on the keyboard and almost never used in names. In 2010, the @ symbol was acquired by the Museum of Modern Art as part of its design collection, honoring its role in global communication.