I need to create an administrative portal that is visually consistent with Office 365 and Exchange online / 2016
What UX experience is most similar to the admin portal in these situations?
I discovered Office Fabric but not sure what else is needed to get an Exchange administrator page.
On
Yes, your research is correct. Office UI Fabric is the front-end framework for building experiences that fit seamlessly into Office and Office 365. Mainly the product made to be replicate Office applications (Word, Outlook, etc.) in 3rd party apps and add-ins. It should be suitable for administrative portal as well, but probably not that reach.
Office UI fabric has two mayor parts: One is Office UI Fabric Core which includes set of style sheets and the second Office UI Fabric JS which delivers built-in components you may use out of box with the core styles.
Office UI Fabric team member here. I'm not sure if Fabric is currently used in the Exchange Admin Portal (I don't think so today), but as Slava points out, Fabric is the framework we use to build many of the apps & experiences throughout Office 365, with many pages and experiences being onboarded all the time. It's your best bet if you want to build a new UX that looks and feels like Office, specifically the Fabric-React components, since we stress-test these in our own products and hold them to a very high standard in terms of performance, accessibility, and feature set.