An email alias is an e-mail address that uses exactly the same mailbox as the original e-mail address. For example, you can have john@domain.com as the authentic e-mail address and add an alias doe@domain.com. Both the addresses will be able to share exactly the same mailbox, so e-mails sent to both of them shall be received in a single place. You can use aliases for a number of reasons, such as emailing different groups of people or signing up on sites. Any time you start getting a lot of spam, for example, you can simply erase the alias while your actual mailbox will not be changed in the least and you will keep the e-mails you need. Aliases in many cases are considered to be a replacement for forwarding e-mails from one mailbox to another one if you are using 2 or more email address for contact on your website.