[otrs] LDAP filter for AD

Hello, I would like to exclude objects from my Active Directory whose DN has the string "NOOPEN" from being taken into account as customers... I have written the following directives at Config.pm: ... $Self->{'Customer::AuthModule::LDAP::AlwaysFilter'}='(!(dn=*NOOPEN*))'; ... $Self->{CustomerUser}={ ... AlwaysFilter=>'(!(dn=*NOOPEN*))' ... But it doesn't work... what is wrong with this filter?