Canonical map problem

Hello, i have a problem with multi domain server. Every time I send to me a email from a virtual domain I receive user@primarydomain.com instead of user@correctdomain.com I have tryed canonical mapping and it works only for user don't appair with the same name in both primarydomain and correctdomain.. Canonical maps file look like : john user@domain.com

If user john appair in both domain i get no email. I have tryed john.domain and john@domain insteat of simple john but it don't work any idea ? Thank you