We control a number of SMTP servers and users that meet certain criteria can send through these servers and therefore exceed Gmail's natural limits. Be as detailed as you can with your answers to improve your chances.

We provide a generous allowance of sending SMTP-based messages before a usage fee is assessed. Details here: https://www.gmass.co/blog/upcoming-price-changes#smtp

Make sure the email address you enter is the same as your Google account. This should be the address you use to log in to your Gmail/G Suite account, and not any alias addresses set up inside Gmail. Also, make sure you've already created a GMass account with that address.