Exchange Admins,
Exchange Administrator of a O365 tenant that is using either DirSync or AADSync are no longer supported and may not work correctly. These tools are no longer supported as of April 2017, and after December 31, 2017 O365 team are not able to guarantee your connections from Windows Azure Active Directory Synchronization (DirSync) or Azure AD Sync work properly.  This may affect your ability to synchronize your local directory infrastructure with Office 365, and will result in users being unable to log in to their Office 365 services.

Recommended action
Azure Active Directory (AAD) Connect is the best way to connect your on-premises directory with Azure AD and Office 365.  Upgrade your sync functionality to the latest version of Azure AD Connect, which is the currently supported tool for syncing data to O365 cloud features.

Hope it helps.

Thanks
MAS
1

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