I have searched for a solution to this only to find lots of issues with regard to scriptting and cmdlets etc.
SBS Console has a tab called reports. Under there you can select new report and there is one called Email Usage which can be emailed to whoever you like detailing how many emails were sent that day and more importantly how big the users mailbox is.
I hope this helps others
regards
Keith
"If you don’t like where you are, move. You’re not a
tree!"