First of all, you should not be using Live Mesh to try to keep an Outlook.pst in sync, though you are actually doing so manually as opposed to trying to sync by making the location into a Live Mesh folder to automatically sync.
I'm not sure why it actually proceeds to 43 megs, but .pst files are blocked from being included in a Mesh. From Help:
Live Mesh also blocks files that have the following file extensions:
- .bak
- .gfs
- .laccdb
- .lnk
- .mbf
- .mny
- .mpc
- .pst
- .sav
- .tmp
- .wlx
-steve
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