[xvolter]

As people already pointed out that your product isn't free, if you require knowledge about a person then they're giving you their information. Facebook doesn't cost a user money, but it costs them plenty else.

For a product with a "free tier" that doesn't work where a user needs to sign up several times, the product itself is flawed.

However, disposable emails again are not the problem, as there are tons of ways to get valid, working emails to bypass any unique email requirements. Blocking disposable emails aren't going to help you with that. The only thing you're removing it a user's access to better privacy. Again, if you require knowing who your users are then you are not a free service.

If you don't care about having users unless you know their real email addresses then you should consider validating their identity in other means, besides an email address. Many services use a text message to validate you also have a phone number that works, which is much harder to anonymize (although I personally have four different numbers for this very reason, based on the trust I give a service I decide which number I want to provide them - since to me, my privacy is worth something, I don't share it for free).