we configured MFA-Server (Installed with Option 2, download in service settings) with RAS functionality at one of our customers. They already uses Office 365. We activated a Azure AD Premium Trial license and everything works fine. Now the test ist over and we like to buy the 'real' license. Which product do we need? I think the "MS Multi-Factor Authentication" will meet the requirements. Or do we have to buy 'Azure Active Directory Premium'?
The link/reference below will help you to differentiate versions of Multi-factor authentication. Since you're using Office 365 already, you may purchase Azure Multi-factor authentication license and assign them to users in Azure Active Directory.