BitBounce is a free service that blocks unwanted emails. In other words, if an individual or entity who has had no prior interaction with you online (such as through email), the sender would have to pay in bitcoins for the email to go through and reach your inbox. This helps reduce spam considerably since most spam email senders won’t bother paying money just to send an email. Curbing spam by charging a fee is not completely new, but BitBounce takes an innovative approach to things and boasts of several thousand users already.