In the case of something like a corporate Exchange server, you can run an IDS/IPS system in front of them to block any specific exploits. Even then, enterprise

In the case of something like a corporate Exchange server, you can run an IDS/IPS system in front of them to block any specific exploits. Even then, enterprise configurations of Exchange are usually quite unique to the company, so there's a low likelihood of a security problem being exposed to the outside.