SOLVED: "User isn't a mailbox user" error when deleting a shared mailbox in an Exchange Office 365 Hybrid

How to fix "User isn't a mailbox user" error when deleting a shared mailbox in an Exchange Office 365 Hybrid using PowerShell Remove-RemoteMailbox

Error when trying to delete a mailbox from Exchange hybrid server

"Username isn't a mailbox user"

The mailbox cant be deleted from the Exchange admin center, but you can remove it with PowerShell

On Exchange hybrid server
Open Exchange Management Shell (run as Administrator)

Remove-RemoteMailbox -identity "user@domain.com"