As Of May 1st 2017 the Office 365 License "Microsoft 365 Business" got some serious Upgrades
What you still might need an E3 License of a P1 Azure Active Directory
- Conditional access (based on group, location, device state, sign-in, or user risk).
- RDS Office activation
- Device objects two-way synchronization between on-premises directories and Azure AD (device write-back).
- Dynamic Groups.
- Group Naming Policy.
- Advanced eDiscovery.