Alias function allows email addressing to the different dept to be forwarded to the different user specified.
(e.g. for domain wmasia.net, if anyone sends an email to firstname.lastname@example.org or email@example.com, this email will be directed / forwarded to any users in the company specified that you want them to receive. Take note that in this case, there is no physical mail account created for the userid hr or sales. This alias only direct / forward mails to other email address specified when someone sends a mail to the above mentioned email)