Send email at buddypress account activation

//send a welcome email when a user account is activated
add_action('bp_core_activated_user','kleo_welcome_user_notification',10,3);
function kleo_welcome_user_notification($user_id,$key=false,$user=false) {
    if(is_multisite())
        return ;// we don't need it for multisite
    //send the welcome mail to user
    //welcome message
    $welcome_email = __( 'Dear USER_DISPLAY_NAME,
 
Your new account is set up.
 
You can log in with the following information:
Username: USERNAME
LOGINLINK
 
Thanks!
 
SITE_NAME' );
    //get user details
    $user = get_userdata( $user_id );
    //get site name
    $site_name = get_bloginfo('name');
    //update the details in the welcome email
    $welcome_email = str_replace( 'USER_DISPLAY_NAME', $user->first_name, $welcome_email );
    $welcome_email = str_replace( 'SITE_NAME', $site_name, $welcome_email );
    $welcome_email = str_replace( 'USERNAME', $user->user_login, $welcome_email );
    $welcome_email = str_replace( 'LOGINLINK', wp_login_url(), $welcome_email );
 
    //from email
    $admin_email = get_site_option( 'admin_email' );
 
    if ( empty($admin_email) )
        $admin_email = 'support@' . $_SERVER['SERVER_NAME'];
 
    $from_name = $site_name;//from
    $message_headers = "From: \"{$from_name}\" \n" . "Content-Type: text/plain; charset=\"" . get_option('blog_charset') . "\"\n";
 
    //EMAIL SUBJECT
    $subject = sprintf(__('Welcome to  %1$s '), $site_name) ;
    //SEND THE EMAIL
    wp_mail($user->user_email, $subject, $welcome_email, $message_headers);
 
    return true;
}