A mailbox alias is an alternate name for your real mailbox, mail sent to your alias(es) will arrive in your mailbox. An alias can be any valid name as long as it is unique in your domain (i.e. you cannot have two people with the name joe@mydomain.com). If your mail account address is, say, michelle@mydomain.com then info@mydomain.com, ms.guenette@mydomain.com and smoothy@mydomain.com could all be valid aliases. Mail addressed to info, ms.guenette and smoothy would all be directed to the mailbox account 'michelle'. You can have unlimited number of aliases on each mailbox account. NOTE: Another use of aliases is to catch all the possible mis-spellings of your e-mail name i.e. you can alias your account to every common mis-spelling.