Not disagreeing with you from the end-user perspective, but AFAIK there are no other solutions that meet all the needs of businesses short of self hosting somet

Not disagreeing with you from the end-user perspective, but AFAIK there are no other solutions that meet all the needs of businesses short of self hosting something like CommuniGate and even that has it's short-comings. Some businesses are trying to use Google and some move back off of it. Corporate email has always been a quadruple edged rusty sword. But I agree it is a nightmare.