Seems like a good time to try convincing the boss we should move our emails to O365. I know he'll say no, but this is ammo for sure.
I don't think that email only justify cost of O365.
I have excellent mail experience with different web hosting providers that provide email service included for a fraction of price of O365.
For example, Hetzner offers 300GB space with unlimited mail accounts for 17 EUR / cca. 20 USD a month.
(I have not used Hetzner's mail services but I have very good experinece with them in cloud/bare metal services)
I mean - you would not convince me to buy O365 with this argument 🙂