I don't know where you keep coming up with that - Email is relatively easy to make highly available, and an Exchange Server in 2014, configured with even a modicum of skill, will likely keep running smoothly for the next 10 years. It's as close to 5 9s, of availability that you can get on a software system.
"There has been no big improvements to the reliability email the last 40 years. "
That's just silly. Take 5 minutes to read through http://en.wikipedia.org/wiki/Email and you'll see what improvements have been made in the last 40 years.
Deliverability of email relies on a number of factors outside your control.
You also mention competance, which is available in variable quantities. You might be able to keep Exchange 2014 running solidly, but I've seen people doing scary things with MS SBS Server 2000 (and the exchange that comes with that).
I don't know where you keep coming up with that - Email is relatively easy to make highly available, and an Exchange Server in 2014, configured with even a modicum of skill, will likely keep running smoothly for the next 10 years. It's as close to 5 9s, of availability that you can get on a software system.
"There has been no big improvements to the reliability email the last 40 years. "
That's just silly. Take 5 minutes to read through http://en.wikipedia.org/wiki/Email and you'll see what improvements have been made in the last 40 years.