thanks for reply
i have it twice
in
wp-content/mu-plugins/domain_mapping.php
and
/wp-content/plugins/wordpress-mu-domain-mapping/domain_mapping.php
i try with a unique copy in wp-content/mu-plugins/domain_mapping.php but i can not find the plugin menu anywhere in wordpress panel.
i supouse that if there is not in plugins folder, i can activate this...
i am confused..