[Wlug] qmail - several domain!

Hi all, I've got my qmail server run so well, it's all nice. Ups, I've got something that bother me alyways! I have several domains hosted in my server where my qmail server running on too, The mail problem is, If somebody send me a message where the address is one of the my listed domain in my server, then.. if I read the mail from one of the available account from my server, here,. I'll receive all the email that attach to my username, so all my email address from the available domain are received in on of the account that I use to open the mail. So, how can I open one of my email address and I just receive the mail that attach to the address where I mean to ? Thanks Man.