Office 365 Hybrid: Mailbox Exists on Both Sides

Modified on Wed, 19 Nov at 7:00 AM

Example user: mcohen

User has a mailbox in on-premise Exchange and also a cloud mailbox.

Our goal is to delete the mailbox on the on-premise Exchange server (i.e. EX2016) and keep only the cloud mailbox.

On EX2016, open the Exchange Management Shell.

Save the mailbox settings to a text file, then disable the local mailbox.

Get-Mailbox mcohen | fl > c:\tools\mailboxinfo.txt
Disable-Mailbox mcohen

Now we tell EX2016 that there is a remote mailbox for the user.

Enable-RemoteMailbox mcohen -RemoteRoutingAddress mcohen@acmecorp.mail.onmicrosoft.com

Add the X500 address from the old local mailbox to the cloud mailbox. Get the X500 address from the TXT file above:

Set-RemoteMailbox -Identity mcohen -EmailAddresses @{add="x500: /o=.......”}