Well, I made an initial decision to keep Red Stamp Mail very affordable. It wasn't built to make money, but rather to help people. But I did not want to make it

Well, I made an initial decision to keep Red Stamp Mail very affordable. It wasn't built to make money, but rather to help people. But I did not want to make it totally free for various reasons - I wanted it to at least cover its operational costs. So the subscription price is very low - $18 per YEAR. This means that most marketing channels are simply too expensive (customer acquisition cost > customer lifetime value). I gave Google Adwords a very serious try, but the results were unimpressive. Other guerilla-ish marketing attempts also did not succeed. So basically the most effective channel is ranking high in search results for relevant terms (e.g. "email for seniors").