E-mails have changed completely the way we communicate with one another. Today, someone in New York can send an e-mail to a friend in Moscow in an easy and inexpensive way. If, for example, user firstname.lastname@example.org wants to send a message to email@example.com, he sends this message to his mail server. The mail server will query the DNS server about the address of the mail server for the valhalla.local domain, and it will send the message to that server. Finally, the mail server at valhalla.local sorts the e-mail and moves the message into thor’s mailbox.