> Is there any way of making a bad email address (eg a spam-trap) reject
> an entire multi-destination transaction?
> If one RCPT TO command is to a spamtrap address, then that message will
> be spam; you do not want it being delivered to any other (genuine) RCPT
> TO destinations.
This may be possible with policy (postfwd and the like) or Milter
protocol, but is not built into Postfix.