Lazyweb - DNS MX query

Is it possible to have email to certain addresses in a domain handled by one mail server, and the rest by another, at the MX record level?

From whatever I can see, it's not: the domain's MX record(s) can only say 'send the lot to there' (with the ability to add 'or there, if that one's busy' via the priority system).

But I'd love to be shown to be wrong.