> The obvious solution is to just bounce invalid recipients, like everybody else.
Yeah, and I've been bitched at and told to "fix that" by The Big Boss, regardless of how I implemented it or any other consequences. Despite being a tech company, they expected the computer to magically know where to send emails.
In this situation, I would have have blackmailed the two, if the guy had been one of the people complaining about email resolution. Revenge is a dish best served very cold.