Absolutely! Amazon’s terms of service allow you to send up to 4 emails to each of your buyers. The founding principal of Rank Booster is that everything follows Amazon’s policies. As long as you lead with a customer support angle, follow their content guidelines and don't try to take them off Amazon. Rank Booster sends your emails through Amazon’s own servers using their secure API so it is just like you were following up with them manually in Seller Central. The most important sentence on their TOS guidelines is: “You may request feedback from a buyer, however, you may not pay or offer an incentive to a buyer for either providing or removing feedback.” Amazon scanning your emails so make sure to follow their guideline as much as possible.