Authenticating users in multi-forest environments is just a bit more complex than doing it in a typical single-forest deployment. You should already be aware of the basics of the different authentication protocols and AD FS, thanks to previous chapters. The configuration of the integration with Office 365 is a straightforward process; with the Convert-MsolDomainToFederated command, you can create everything that's needed in your AD FS configuration. With the SupportMultipleDomain switch, you can define whether you're using a multi-forest scenario.

Next, we'll start with the supported and possible scenarios in the case of using multiple forests and Office 365. We'll focus on the AD FS server deployment. Furthermore, you can always attach an AD FS proxy/WAP to these...