Hi Robert,
I'm in a similar boat as you and wonder if you have the same setup we are going through right now. Since you mentioned an email compliance policy, I believe you have an SEG. Correct? And is your MS Exchange on-premises or hosted in the cloud?
In my case, we have MS Exchange on-premises and SEG on the backend with a native mail client on mobile devices. We are rolling out Outlook app but due to lack of support for Exchange Active Sync with such app, we have to set up Workspace ONE Access (or Identity Manager) along with turning on modern authentication in Exchange. I wonder if you have the same or similar setup as me.
Tom