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

LEGOFFanthony can you try running it again? I've seen at least one report of this as a transient error (in Powershell Management API not the cmdlet itself), rerunning again later it worked. You should also be able to create an enforcement pause via the EAC report (Reports > Mail flow > Out-of-date connecting on-premises Exchange servers). 

janakkhadka the current enforcement scope only applies to the connecting server used to connect to EXO over an inbound connector of type OnPremises. So upgrading your Edge server to 2019 will obviate the risk of getting throttled/blocked by this specific initiative. However, as you can imagine we strongly encourage folks to upgrade all their out-of-date Exchange servers regardless where they are in your environment.

Deleted check your PMs for a message from me.