You can integrate Office 365 with your existing directory services and with an on-premises installation of Exchange Server, Skype for Business Server 2015, or SharePoint Server 2013.
- When you integrate with directory services, you can synchronize and manage user accounts for both environments. You can also add password hash synchronization or single sign-on (SSO) so users can log on to both environments with their on-premises credentials.
- When you integrate with on-premises server products, you create a hybrid environment. A hybrid environment can help as you migrate users or information to Office 365, or you can continue to have some users or some information on-premises and some in the cloud. For more information about hybrid environments, see Office 365 hybrid cloud solutions overview.
You can also use the Azure AD advisors for customized setup guidance: