Field Notes

Link a Synced Active Directory User to an Existing Microsoft 365 Mailbox in a Hybrid Environment

  • Billy Ford

In this scenario, an on-premise AD user was created and synced with Microsoft 365. The Microsoft 365 user has an Exchange Online mailbox, but this mailbox is not visible in the on-premise Exchange Admin Center.


Obtain the GUID of the Exchange Online Mailbox

  1. Open PowerShell and connect to Exchange Online.

  2. Use the Get-Mailbox command to obtain the GUID of the user's existing mailbox in Exchange Online. Save the GUID for use in the next section.

    Get-Mailbox jdoe | Format-List ExchangeGuid
    ExchangeGuid : < ExchangeGuid >

Update the On-Premise Exchange Environment

  1. Open Exchange Management Shell on the on-premise Exchange server.

  2. Use the Enable-RemoteMailbox command to mail-enable the on-premise user. The -RemoteRoutingAddress parameter value will be the user's @<tenant> SMTP address.

    Enable-RemoteMailbox jdoe -RemoteRoutingAddress
    Name        RecipientTypeDetails    RemoteRecipientType
    ----        --------------------    -------------------
    John Doe    RemoteUserMailbox       ProvisionMailbox
  3. Use the Set-RemoteMailbox command to update the GUID of the on-premise mailbox to match the GUID of the mailbox in Exchange Online. Use the value obtained in Step 2 of the last section.

    Set-RemoteMailbox jdoe -ExchangeGuid <ExchangeGuid>