I saw this on the documentation website: "Note: The limits for email link sign-in emails were recently changed. Please add a billing instrument to go beyond 5 email link sign-in emails."

It's really strange that you quietly set the limit of sign-in emails to 5. Why? It makes no sense. For testing it's too low, and for production of course.

First you hook developers up to Firebase and then you quietly lower the limits. Good business practices.