Aliases are a way of making one email account seem like many. This is called “unlimited aliasing”. Suppose you are in charge of billing and marketing. Instead of making two individual accounts to handle these emails, you would make one account named You@Yourdomain.Com which is a valid POP account, at which you can send and receive mail.. Next you would apply Billing, and Marketing as aliases of the You@Yourdomain.Com account. With this setup, mail sent to any of the 3 above mentioned email accounts (Billing@Yourdomain.Com, Marketing@Yourdomain.Com and You@Yourdomain.Com) will all be sent to the mailbox of You@Yourdomain.Com.