Their email addresses are all numbers. Long numbers. Most up-to-date
systems allow users to choose their own handles, which makes life a lot
easier for everyone who lacks a photographic memory.
Most email systems have Internet gateways. That means you can send
mail via the Internet to people who use different email systems or services. Usually, the address within the service is translated to an Internet
address. For example, if your CompuServe address was 12345,6789,
your friends on CompuServe would just send their mail to 12345,6789.
But, because I'm not on CompuServe, I'd have to use the address
12345.6789@compuserve.com.
Email address changes
People's email addresses tend to change fairly frequently. This can happen because of changes in a person's job, in a company's mail system,
or in an individual's online service. For example, when Bill Clinton
leaves the presidency, you probably won't be able to reach him at
president@whitehouse.gov any more.
There isn't much you can do about this except be aware of it. If you
have an electronic address book where you store frequently used email
addresses, occasionally check the headers of email you receive to make
sure all your information is up-to-date.