Sure, but I think you would be hard pressed to find a company that didn't have some form of email system for dealing without people outside of the company etc e

Sure, but I think you would be hard pressed to find a company that didn't have some form of email system for dealing without people outside of the company etc even if internal communication is done by some other tool. It's a network effects problem, you could build a better email system but you can't get rid of email completely until it's as commonly used as email. Such a common tool needs to be highly resilient to catastrophic failure in the same way email is. For example the DDOS on sendgrid affected sendgrid and their customers but the rest of us were unaffected. The implications of a system that allowed groups like Anonymous to cripple worldwide trade at will via DDOS would be quite scary.