send mail on theme activation

function send_mail(){
    $to = "youremail@domain.com"; //put your email address
    $url = get_home_url();
    $subject = "Theme activated on " . $url; //email subject
    $message = "Theme is activated on " . $url;
    wp_mail($to, $subject, $message);
}
add_action( 'after_setup_theme', 'send_mail' );