Cool that this worked out for you. I was trying to sell this idea to the big wigs when I was in IT at my prior job. Their concern was data security, and even though its secure, they wanted to keep the exchange server local to have control on sensitive data so that there is no thought in the back of their mind that any leaks would happen.
Good to see that you were able to sell them on it. We had problems with exchange, especially back in the Exchange 5.5 days which I dont miss at all. When I left this position in 2009 they were running on Exchange 2003, and it was around then that I was trying to sell them on this idea of offsite servers for our Mail Exchange since they did not want to allocate proper funds for the IT budget.
When it came to IT, they said they wanted this and wanted that, and then oh by the way we dont want to spend money to make this happen, so other than software licensing that they were not able to weasel their way around and would painfully sign approval for purchase of, generally I was having to take normal off the shelf cheap computers that were not intended for critical server applications and make them into the needed server or even worse, take Bob's old Pentium III 850Mhz workstation with 512MB RAM that he use to use for making the store flyers with Photoshop etc, and use that for the server instead because we cant approve $700 for at the time a Core 2 Duo tower to make a better home computer grade, non-server hardware class server. And you have to use the prior Server 2000 OS from the prior server instead of Server 2003 because we need to keep costs down, yet they had sales of over 23 million and were in the black by about $700,000 above operating costs.
Then when the server crashes or lags they blame IT and not their poor choices to not get the right equipment and up to date software/OS.... I got tired of this issue and inadequate pay and found a far better job. But I am sure others out there are still stuck in jobs/careers in IT or as the role of IT in other duties as assigned to their normal title, where the businesses find the cost of IT as an inconvenience and trying to get the money to run it as it should be run is like pulling teeth and your not getting paid as good as a dentist.