What is the minimum annual overhead required to admin an On-Premises Exchange Server
Solution 1:
A data point.
I manage about 24 Exchange servers for customers now, and spend about 2 hours per month on mail-related issues which may include SSL certificates, user management, managing the Barracuda cloud spam filtering and disk space/backup maintenance.
Exchange is pretty hands-off for me post-install, however, the ramp up to installation/deployment is very time consuming.
These are all simple single-server Exchange environments with 250 users or less.