Backing up PST files to OneDrive: need a way of getting the local OneDrive folder to release the space automatically

Question

I'm backing up PST files to OneDrive (but definitely never opening them in Outlook there).

This works fine except that I don't seem to be able to get OneDrive to release the local space automatically, which is a problem given I am doing all this on a 128GB Surface.

I run a powershell script as follows:

get-childitem . -Force -File -Recurse |

where Attributes -eq 'Archive, ReparsePoint' |

foreach {

attrib.exe $_.fullname +U -P

}

to tell OneDrive to release the local space for my backups in general, and it works perfectly with everything except the PST files.

(BTW I do the backups using robocopy which rightly refuses to copy the PST file if it's open in Outlook.)

Any ideas what might be going wrong here? Or is there perhaps a non-powershell automated mechanism I can use?

I initially posted this in the Outlook category in Community but was told to come here instead.