The at sign, required character of the e-mail address.

An e-mail inbox full of spam e-mails

Electronic mail (or e-mail or email) is an Internet service that allows people who have an e-mail address (accounts) to send and receive electronic letters. Those are much like postal letters, except that they are delivered much faster than snail mail when sending over long distances, and are usually free.

Like with regular mail, users may get a lot of unwanted mail. With e-mail, this is called spam. Some programs used for sending and receiving mail can detect spam and filter it out nearly completely.