BoardThreads - Sell Project

The user chooses a Trello list to register in the app and an email address @boardthreads.com to relate with that list. All emails sent or redirected to the chosen address will create a card in the selected Trello list. Comments on that card will be returned to the original sender as emails, and that conversation can keep going. The only comments that get sent as emails are those marked with an envelope emoji (namely, :email:, :envelope: or :e-mail:, on Trello), so you can comment internally and discuss the issue with your team. A lot of corner cases are covered (for example, more than one people responding to the same email thread, or notifying, in the Trello comments, if the submission has gone for some reason), but not all. Users can choose to send and receive email through their own domain, instead of using the @boardthreads.com address. Automatic signatures are supported: the user may define a signature template and that will be rendered with the Trello name and/or username of the actual replier (so each teammate that replies to an issue can be properly identified). Outgoing email is possible, but only for one recipient, for now (the user must create a card, add the @boardthreads bot to it then name it using the BoardThreads template "<subject> {<target email address>}", the bot will notify in the comments if you did it right) -- In production for almost 3 years now, but revenue is small, and I don't know how to market it. Visitors average 7 per day (without any marketing, I don't know from where are these people coming), 1.5 times each month someone tries out the app using the test Trello board (people send an email to the test address, go to the public board and reply to themselves) and about once in every two months someone starts using the service, eventually (maybe once in every 6 months) someone starts paying for it. There are currently 5 paying customers using the app (besides myself. I've used it heavily on https://formspree.io/ for the entire life of the project, but the team is planning to moving to some other app there, something that supports bulk emailing, notifying all the users etc.). There are, however, at least 3 users that are using it for free because I offered 2 months of trial period in the landing page, but never put a system to restrict access and usage after 2 months, so basically the users who pay only pay because of their sheer honesty (last week one of these free riders emailed me asking why there was a notification in the dashboard about a trial period that had ended, and asking me if he could create another address).