If you use the Barracuda Message Archiver Exchange stubbing feature and plan to migrate your data from a Barracuda Message Archiver appliance to a cloud service, you must unstub your data prior to mirroring it to the cloud. Unstubbing a message allows the Barracuda Message Archiver to restore stubbed attachments to the copy of the message in Exchange.
Stubbed mail stored in a cloud service can cause problems such as data loss. For example, if you need to unstub your mail that is in the cloud, the Barracuda Message Archiver might not be able to find the full message. Also, while the data still resides on the Barracuda Message Archiver, in the event that you do not have access to the appliance, you will not be able to unstub your mail.
Before you mirror data to the cloud, contact Barracuda Networks Technical Support for direction on unstubbing mail currently stubbed to the Barracuda Message Archiver and restoring that mail to your Exchange server. This will ensure that your data is replicated successfully.