Sorry, there is no way to do that. If everyone followed the rfc's exactly, the mail would be delivered or returned. That might take days or even weeks. But lots of sites just silently discard undeliverable mail. If your servers are not configured correctly, the mail can arrive at a destination host without a vaild return address. Spammers do this intentionally. (A spammer once sued AOL for returning undeliverable mail as per the rfc's.)