Found out that if a pst file is in use by Outlook, and the file is located on a NAS which is both CIFS enabled and NFS enabled, I can’t rsync the file!
rsync: read errors mapping “outlook/outlook.pst”: Permission denied (13)
ERROR:outlook/outlook.pst failed verification — update discarded.
Looks like I’ll have to schedule a time with the user to turn off outlook. Hopefully, I won’t run into any corruption issues =\.