Hi, I am Janko from Serbia and I used to work for UK-based outsourcing company where we maintained several hundred domain controllers and Exchange servers, and among them several dozen Exchange + BES servers, and I have also set up Exchange + BES via freelancer projects several times, I believe it is still visible in my project history here at Freelancer.com. Exchange is always resource hungry, therefore I would recommend dedicated server for itself, BES and PGP servers can go to VMs each (separate one for both), and depending on the number of users and expected volume of traffic we would discuss specific server specs later on.