Dana Gardner, founding analyst of InterArbor Solutions said most enterprises and SMBs (small and mid-sized businesses) deal with e-mail outages internally with some regularity, noting that the rates of uptime for these non-transactional apps can be as low as 97 percent
and still be considered mission-critical. He told me:
So let's take a reality check on whether Web-based apps are or should be any better than behind-the-firewall apps such as e-mail that sometimes go down. That said, trust and value are essential for any migration to Web-based or cloud-provided apps. The bad news is that if Company XYZ has an e-mail outage, people go to the water cooler and chat about the Olympics and shrug it off. Few people outside the actual company know or care. But when Web mail such as Gmail goes down, it's for the world to see.
(emphasis mine - DWM)