Because I couldn’t find an answer to this issue anywhere else, and Microsoft Support was unable to determine the root cause I’m sharing this with you. During a cutover migration from Exchange 2003 to Office 365, my batchjob failed after the initial sync and was unable to process incremental syncs of emails in Exchange 2003.
The error in the batchjob’s status display for each failed user was:
ProvisioningFailedException: The name “XXX” is already being used. Please try another name.
Solution: delete the batchjob and all the users it provisioned. Recreate and run it again, and this time, don’t edit the primary SMTP address of these users while the job is running, it is used as a foreign key to match between Onprem and Office 365 and confuses the batchjob if it is changed.
The hint I got that gave me an idea of where this issue was coming from was the following error I received a few times (but not consistently) when changing the primary SMTP address of each user:
You can’t use the domain because it’s not an accepted domain for your organization.
The domain was fully validated and the email was not assigned to any other user.
So, don’t mess around while a batchjob is still running 🙂