If you click on the Sales tab, then on Transactions, you will get a listing of the sales. On the far right of each item is an option of Email Buyer. When you click on that, a little menu shows up where you can select whichever email (request address, request payment, etc.) you want to send, and then you can go from there. I haven't seen a way to do that en mass... perhaps I've missed instructions for it, or maybe someone else will read your post and supply the information
Hope this helps.