Convert resource mailbox to cloud only

Hi PSonander,

here's a detailed step-by-step guide on how to convert on-premises resource mailboxes to be cloud-only in an Exchange Online (hybrid) environment:

Note: This process assumes that you have already migrated the resource mailboxes to Exchange

Online as part of your hybrid deployment.

1. Backup Data: Before making any changes, ensure you have a reliable backup of the data associated with the resource mailboxes. This includes emails, calendar items, and other mailbox content.

2. Verify Mailbox Locations:

   • Confirm that the resource mailboxes are currently synchronized and available in your on-premises Active Directory.
   • Ensure that they are accessible in Exchange Online and are functioning as cloud-only mailboxes.
   • You may need to disconnect the mailbox from the on-premises user account. To do this, use the Disable-Mailbox cmdlet in your on-premises Exchange environment. This cmdlet removes the mailbox from the on-premises Active Directory user account without deleting it. For example:

Disable-Mailbox -Identity "OnPremUser"

• Recreate Mailbox as a Cloud-Only Mailbox:

  • After disconnecting the mailbox from the on-premises user, you can create a new cloud-only mailbox for the resource. This is typically done in Exchange Online PowerShell. Here's an example of how to create a new mailbox:
   

   

New-Mailbox -Alias "CloudResourceMailbox" -UserPrincipalName "email address removed for privacy reasons" -PrimarySmtpAddress "email address removed for privacy reasons" -DisplayName "Cloud Resource Mailbox"