Copy and paste the code in functions.php of your current theme. Add your custom email template.
// Remove the container section in trackform
remove_filter( 'wp_new_user_notification_email', 'wpcfe_wp_new_user_notification_email', 10, 3 );
add_filter('wp_new_user_notification_email', 'custom_new_user_notification_email', 10, 3 );
function custom_new_user_notification_email( $wp_new_user_notification_email, $user, $blogname ){
$user_login = stripslashes( $user->user_login );
$user_email = stripslashes( $user->user_email );
$headers = array('Content-Type: text/html; charset=UTF-8');
$headers[] = __('From: ', 'wpcargo-frontend-manager' ) . get_bloginfo('name') .' <admin@no-reply.com>';
$login_url = wp_login_url();
$message = "<p>".__( 'Hi there,', 'wpcargo-frontend-manager' ) . "</p>";
$message .= "<p>".sprintf( __( "Welcome to %s! Here's how to log in:", 'wpcargo-frontend-manager' ), get_option('blogname') ) . "</p>";
//You can add custom message here...
$wp_new_user_notification_email['subject'] = sprintf( '[%s] Your credentials.', $blogname );
$wp_new_user_notification_email['headers'] = $headers;
$wp_new_user_notification_email['message'] = $message;
return $wp_new_user_notification_email;
}