We are in the middle of moving from EAS (a 3rd party email archive solution) to Exchange 2013 Online Archives. During one of the initial migrations (using Globanet Migrate software) a user had his archived messages duplicated up to 7 times each into his Online Archive equaling close to 70GB of data.
My question is what is the best way to remove the duplicate items? We are using Office 365 Pro Plus with on premise Exchange 2013. It seems one feature that would work fine would be to use the "Clean Up Folder" option in Outlook, but for some reason this is grayed out for any of the Online Archive folders. Another option might be to delete everything out of his archive and remigrate, but we have every mailbox on a permanent, in-place hold so that "deleted" data would never get purged from the system, and I would add more data on top of it doing another migration.
The big thing is finding something that works with Outlook 2013 and Online Archives whether it be a PowerShell script or a Outlook plug-in. Any ideas would be appreciated!