The cost to you is minimal. But something else was needed for e-mail to work. Other standards were developed so that a person could send a message to someone else via the Internet. This standard makes it possible to send e-mail to someone else. In 1982, there was just one e-mail program, the unix mail program.
Today there are many, and they can do different things and they have different commands.
However, there are some things that all mail program can do. Likewise the Internet relies on the Internet address to get mail from one computer to another. At symbol 3. In the example above miles is the user ID, marcie is the system, sosu is the institution, and edu is the highest level domain. User ID now consists of the individual's first name initial, plus as much of their last name that will fit in the 12 character limit 2.