AD Authentication with Office 365

We can off-load authentication in WP to some other internet accessible process through the use of the “authenticate” filter hook. In fact, the entire WP authentication function could be overridden if need be, though the filter is usually enough. So on the WP end, there is a way, though it might require custom coding. It depends on what process is doing the authentication. This is typically done through some sort of API.

I don’t know much about Office 365. You should ask through an Office support forum what sort of API is available for authentication from an external server (your WP server).