I have found the following article that tells me how to restrict the number of recipients for an entire exchange organization, receive connector, hub transport, and per user basis.
However, I have about 300 users out of 1,200 or so that I want to limit to 10 recipients. We currently have a dynamic distribution group setup for these users, but I can't use that as my basis to set the rule. I've also tried a security group and that too doesn't work.
Is there any easy alternative to setting this for a group of users instead of doing it on an individual basis? I will have other users later on that I'd like to have auto added as long as they are in a certain OU or group member.