We have a server that sends our weekly newsletter to subscribers, To prevent people like Hotmail or Yahoo from blocking us due to sending too many simultaneous emails to them, Is there a way we can stagger email, or rate-limit outbound emails from postfix?

Keep in mind, I dont want the mailserver to stop queueing mail or accepting new messages, Simply defer delivery if there are more then 3-4 messages per destination domain/ipaddress, or something similar.

Note: I dont want a Sender Throttle, as described in a similar question, here. I'm looking more for a recipient throttle but haven't had any luck finding out how to do so with PolicyD or Anvil services, and was wondering if anyone else has accomplished such a task.