I don't see pricing anywhere on the website. Also, you never explicitly say that it is free. This is concerning.
Of course, I could make a separate throwaway email, but then the main benefit if this service (convenience) disappears.
Lack of a clear monetization model makes my inner paranoid even more concerned: looks too much like an attempt to collect emails for some nefarious purpose. Why else would you allow literally anyone to just burn your money? OpenAI API is not that cheap.
Sorry, maybe I'm just not in the target audience.