Error Message

Cannot move items to the Virtual Vault, error: You cannot modify the contents of a managed folder.

Folders are identified as being Managed by additional MAPI attributes that are added to the folder(s) when assigned:

PR_MANAGED_FOLDER_COMMENT
PR_MANAGED_FOLDER_ID
PR_MANAGED_FOLDER_INFORMATION

If a mailbox is removed from a Managed Folder Policy, by default these attributes are not removed from the folders within the mailbox container(s).

Below steps can help to remove the above additional attributes still associated with these folders.

1. Start the Exchange Management Shell.
2. Type the following command:

Set-Mailbox -Identity "DOMAIN\USER" -RemoveManagedFolderAndPolicy

Note: This will remove all folders that were managed in this mailbox unless current data resides in said folders.  If items do reside in a previously managed folder, the Managed Folder properties will be removed, leaving a standard folder.

See the following Microsoft Article for details:

https://technet.microsoft.com/en-us/library/aa998580(EXCHG.80).aspx  
Turning Off Messaging Records Management

3. Once the Managed folder MAPI attributes are removed from the associated folder(s), this change must be updated to Enterprise Vault (EV). This can be achieved by Synchronizing the mailbox with the option "Folder hierarchy and permissions" checked.

4. Synchronize the Vault Cache for this user so the change is reflected in the Virtual Vault of the user as well.