This should answer your questions, you should also visit the site as there is a form you need to complete with-in a certain time frame.
Sales for out-of-state delivery:
Sales where the purchaser accepts title to and possession of an item outside Massachusetts generally are exempt. Similarly, if a vendor is obligated to deliver to an out-of-state purchaser’s address or to an interstate common carrier for such a delivery, the sale is not taxable in Massachusetts. Generally, however, any taxable item brought into the state within six months of purchase for use, storage or consumption in Massachusetts s subject to the use tax.
Check this site A Guide to Sales and Use Tax