user_verification_mail_vars

add_filter('user_verification_mail_vars', 'user_verification_mail_vars_11012021', 2, 10);

function user_verification_mail_vars_11012021($vars, $user_data){
$user_id = isset($user_data->ID) ? $user_data->ID : 0;
$mr_or_mad = get_user_meta($user_id, 'mr_or_mad', true);
$vars['{mr_or_mad}'] =$mr_or_mad;

return $vars;

}