About once a month, I get asked why “When I log off my machine, why do I get a load of sync errors?”
Well, that is because Microsoft offline files is attempting to protect you from syncing files such as database (mdb) files, or outlook data files (pst).
I looked to see if there was a way to tell the system to stop showing the error on the sync when you logoff your PC (because I would prefer not to synchronise unsupported files), but that is not possible.
Therefore you have only one option and that is explained in this Microsoft Article. It explains how to create a policy which you can add to the “Small Business Server Folder Redirection” policy, or create a new one specifically for this.