multi domain

[Alex]

Hi all,
I have some problem in setting up krb5.conf for client authentication.
I'm working on a multi domain scenario with several domain like
A.COMPANY.COM, B.COMPANY.COM, ... and one kdc server (Active Directory)
that belongs to A.COMPANY.COM domain.
So I setup a krb5.conf as follows

[libdefaults]
        default_realm = A.COMPANY.COM

[realms]
        A.COMPANY.COM = {
            kdc = kdcserver:88
        }

[domain_realm]
        .a.company.com = A.COMPANY.COM
        .b.company.com = A.COMPANY.COM
        a.company.com = A.COMPANY.COM

Principals that belongs to A.COMPANY.COM are authenticated (kinit
works), others not.
For those who are not authenticated kinit returns "Client not found in
Kerberos database" error message but user exist in AD.
Any suggestions or how I can get more information would be appreciated.

Thanks, 
Alex