Hi There,
I have very live experience what you are looking.. Since, i have worked for such things in very advance level. Let's chat more about..
I have ended up even providing OTR & ECC chat application as well.
I did the setup from Network, Security, pfSense firewall, Exchange , BES5, BES12 and much more.
We can discuss it more if you like my words above. Please don't hesitate to ask me if any questions before assigning it.
Thanks,