Comment by coreylane

Major US banking apps I've used in the past 7 or so years already support mailing physical checks directly from their mobile apps via their bill pay service. Just add someone's physical address as a "payee", create a payment, and it sends them a check in the mail, for free. Perhaps your app is slightly more convenient and has more advanced features which make it worth the fee, but it seems like a problem already mostly solved and widely available.