MigrationPermanentException: Cannot find a recipient that has mailbox GUID

Moving a cloud mailbox back on-premises fails because the on-premises remote mailbox does not have the matching ExchangeGUID.

Why it happens

To move a mailbox, ExchangeGUID must match on the Exchange Online mailbox and the on-premises remote mailbox. When a mailbox is created directly in Exchange Online, the GUID is not written back to the on-premises remote mailbox, so it shows as all zeros.

How to fix it

1. 1

   Step 1

   In the Exchange Management Shell on-premises, check the remote mailbox. A value of all zeros means the GUID is missing.

2. 2

   Step 2

   Connect to Exchange Online PowerShell and read the ExchangeGUID of the cloud mailbox.

3. 3

   Step 3

   Stamp that GUID on the on-premises remote mailbox with Set-RemoteMailbox.

4. 4

   Step 4

   Run a directory sync, then retry the move.

5. 5

   Step 5

   To avoid this in future, create mailboxes on-premises first and then move them to Exchange Online.

Get-RemoteMailbox user | Format-List ExchangeGUID
Get-Mailbox user | Format-List ExchangeGUID   # in Exchange Online
Set-RemoteMailbox user -ExchangeGUID "<GUID from Exchange Online>"
Start-ADSyncSyncCycle -PolicyType Delta

Source

Full guide: How to migrate from Exchange Server to Exchange Online →