Here be dragons
"The final decision is made by non-technical staff."
This is a recipe for disaster. Polish up your CV and check what colour your parachute is.
Seriously.
Decisions need to be made by technically competent people and if nontechnical people are involved it must be simply to sign off on those decisions.
$orkplace has so far spent £5+ million pounds and 3 years migrating from a slightly broken(*) locally administered unix/exim setup to Office365 ("But it's Free!") - and ended up with a substantially inferior system (much higher levels of support handholding required) - thanks to a decision effectively made via conversations and handshakes on the golf course ("But it's FREE!")
Justification: The new system is "FREE" - technically yes, but it's also broken(**) and is incurring 20 times more support manpower than the old one did.
(*) Slightly broken = overloaded and manglement wouldn't spend money upgrading the storage/frontend, resulting in increasing amounts of downtime during peak hours.
(**) Limits on the number of connections mean that users are seeing effective downtime in increasing amounts during peak hours - and there's no way of increasing the limits as it's all in the hands of a third party. That's on top of the system often taking 12-20 hours to deliver messages which have arrived during peak hours.