There are 3 main “backup” type files in QuickBooks.
The Backup File “.QBB”
The Portable Company File “.QBM” – smaller file, easier to send but takes longer to create
I don’t use either of these to send QuickBooks files. I simply use a service like http://www.yousendit.com and simply send the “.QBW” which is the full “QuickBooks Working file”.
The Accountant’s Copy “.QBA” – allows you to set a dividing date so your accountant can work on the past and make adjustments while you continue to keep up the day to day bookkeeping going forward.