you don’t have to provide an address … you generate a token on their site, print it out, put it in an envelope and send it with cash to them.
they receive the cash and activate the token based on the cash provided with it
see their faq Can I really pay with cash?
You bet, and please! Stay anonymous all the way. Just put your cash and payment token (randomly generated on our website) in an envelope and send it to us. We accept the following currencies: EUR, USD, GBP, SEK, DKK, NOK, CHF, CAD, AUD, NZD