submission message quota

[Gerry]

Hello,

I am trying to come up with a way to have individual quotas per user for
the submission service. Similar to what I could achieve with Postfix and
policyd.

More specifically, the quota I am most interested in, is limiting the
number of messages a single account can send within a given timeframe.
Ideally, I'd also like to limit the number of total recipients within a
given timeframe, to mitigate the loophole of adding multiple recipients
to a single message.

Example: account Y is allowed to send 500 messages per 60 minutes, with
a maximum of 2000 recipients overall.

What would be the best path to take?

Thanks!

Gerry