Enable Remote Mailbox CSUser Office 365

Enable Remote Mailbox CSUser Office 365


When you work with an hybrid deployment of Office 365, new object creation is a bit tricky, depending on where they will land. Indeed, you can’t create a user directly in Office 365 and hope for the best. This won’t work because your Active Directory is still the start of authority of your users attributes.


When you create an Office 365 mailbox, without using the local Exchange portal/PowerShell, the Exchange Online mailbox won’t be seen by your local Exchange organization. That will cause issues about:

  • Autodiscover
  • External incoming mail flow
  • Global Address List
  • Calendar Sharing
  • Mailbox delegation

The fix is to enable the remote mailbox from your local Exchange servers. To do that, start an Exchange Management Shell and type:

Enable-RemoteMailbox -PrimarySmtpAddress RemoteUser@ItForDummies.net -RemoteRoutingAddress RemoteUser@itfordummies.onmicrosoft.com -Identity RemoteUser

Note: The remote routing address is the technical email address generated by Office 365.


You can do the same kind of thing for Skype Online:

Enable-CsUser -Identity RemoteUser -SipAddress 'sip:RemoteUser@ItForDummies.net' -HostingProviderProxyFqdn 'sipfed.online.lync.com' -verbose

This will also allow people from Skype OnPrem to be able to Skype people on Skype Online. If you don’t do that, the impact is much more present. The Skype client won’t be able to connect, users won’t be able to chat with someone outside of their Office 365 tenants.


When creating an online user in an hybrid deployment, you should always use the on-premise tools to do it. Otherwise, you will need to run the PowerShell lines above to fix the Active Directory attributes on your local deployment, that will be synced to Azure AD with AADConnect.

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