Recaptcha is mainly used to protect websites from spam and abuse. This is to ensure that all your subscriptions are authentic and not bot controlled.
How to enable Google Recaptcha:
Create an invisible Recaptcha client and pass the client keys to support. There are 2 keys that need to be created. (Site Key, Secret Key). Ensure you share the keys securely in an encrypted file/google document.
If Google Invisible Recaptcha is not enabled in your site, your custom domain setting displayed below won’t apply to your site. i.e, if you have enabled “Allow customers to checkout without payment details” under Checkout and Self-Server Portal this setting may not apply until Google Recaptcha is enabled from the backend by support.
Note: This requirement is necessary only for the above particular setting highlighted.