any chance for a delta copy option?

[REZ]

Outlook PST files are easily 20GB these days.

In addition, breaking down the outlook.pst to individual pst still contains 20+GB of cumulative pst files. When emails are moved into individual pst files, FFS still has to copy over all of these pst files in total because outlook updates all of the individual pst files even if you didn't move any emails into them. If I'm not mistaken, just the act of having the individual psts listed in the tree will cause their datestamp and database header to be modified each time outlook is opened.