How can I send email to an email stored in a custom post type?

Question

//Sending Email

add_action( 'transition_post_status', 'notify_author_on_publish', 10, 3 );
function notify_author_on_publish( $new_status, $old_status, $post ) {
    if ( 'publish' !== $new_status ||
        $new_status === $old_status ||
        'directories' !== get_post_type( $post ) ) {
        return;
    }

    // Get the post author data.
    if ( ! $user = get_userdata( $post->post_author ) ) {
        return;
    }

    // Compose the email message.
    $body = "
            Hi ".$author->display_name.",

            Your listing, \"".$post->post_title."\" has just been published.

            Reserver a Booth! https://example.com/

            Thank You, Admin";

    // Now send to the post author.
    wp_mail( $user->user_email, 'Your listing is published!', $body );
}

Here is my code that is sending email to author of the post on post published BUT I want to send email to a specific email address stored as contact-email in this custom post.

Help me....Thanks ahead.