Locally hosted Exchange is insanely wasteful. Organizations continue to believe that a $25 lock on some closet is "more secure" than a real datacenter and insist on paying 3+ intermediaries' markup on outrageously expensive software licenses and servers, racks, UPSes and other accessories. They buy servers which they barely use, and what cost savings there is gets wiped out by VMWare licensing fees if they decide to do virtualization. Then they've got to pay another company to bring technicians out to maintain the server, change the UPS batteries, etc, at a cost of $100+/hour.
All of this could be so much more cost-efficient at scale. GMail may be a privacy concern, organizations' insistence on hosting their own email is maddeningly, mind-bogglingly wasteful considering they could get the same functionality for a few hundred bucks a year.
Someone needs to make a real open-source competitor to Exchange so people who insist on hosting their own stuff can at least stop throwing away money that could employ people on Exchange licenses. I understand that IMAP exists, but no one actually wants to use Thunderbird.