Server 2019 throttle outgoing mails

Brass Contributor
Hi all!
Environment: We have a hybrid deployment. I need to throttle a user outgoing mails on the on-premise servers. We are using 2019 version, a mailbox and a sperate edge server.
Goal: Throttle e-mails sending 2 email/minute, for test user. I do not know what happens exactly when the throttling happens. The goal is the server to accept more emails than 2 email/minute than send out them not as one big bulk mail but with some delay. For example if you send one mail with 10 recipients, send the mails out 2/mail/minute.
Actions: Created test user, crated test throttling policy. Set the test policy on the test user. The policy is copied from default. Modified parameters are message rate limit: 2, owa max concurerency: 1.
The messages are still not throttled. What am I missing?
I know the policy is not taking affect immediate, it is already did, tested with recipient rate limit.
Or somehow should I use, some connector limits? Or modify the whole server back pressure limits (if it is possible) like number messages in submission queue? 
Any ideas are welcome. 
1 Reply
We used a non Exchange solution with unique MTA. Question irrelevant.