Hello, one of our clients just changed their ISP and are now having trouble sending to certain domains. Most of them are government domains. We changed the reverse dns and the spf so we are certain that all is well there. We also verified that our client's IP is not blacklisted. When they send to certain domains, they get a bounceback saying "requested #550 denied by policy ##". We originally thought this was an issue with the receiving domain - however the originating server is that of our clients so I assume the problem is on our clients end. Any help would be appreciated. They are running an SBS 2008 server with Exchange 2007.