We have a new option those who use DirSync for directory synchronization with Office 365. It monitors the staged delete updates that are to be sent to Azure AD and if they exceed a limit that you define then the delete operations are held until you review. This can help you to avoid accidental mass deletion of accounts from Azure AD. Details of how to set this up are here: http://social.technet.microsoft.com/wiki/contents/articles/24544.how-to-avoid-syncing-accidental-deletes-to-the-cloud-directory.aspx 

This requires version 6765.0006 of DirSync. Version history is listed here: http://social.technet.microsoft.com/wiki/contents/articles/18429.microsoft-azure-active-directory-sync-tool-version-release-history.aspx

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