Throttling and Blocking Email from Persistently Vulnerable Exchange Servers to Exchange Online

For people with a dependency on legacy systems, we get backed into a corner with these constraints, only to realize that the only server architecture or product that is NOT covered by inclusive support is Exchange Server. Typical.

The 2016 server I had to install in my environment won't relay outbound for inexplicable reasons, and we're all out of time since you only get 90 days per calendar year. 

I've got no choice but to deploy postfix at this point since Exchange support has to be purchased in blocks of 10 hours.