I just had a company refuse to send to mozmail.com, thought they managed to charge the credit card just fine and the email address didn't throw an error on sign up. Figured it out on phone with support so they have a record of exactly why they lost that sale worth a few thousand dollars. I'd like to think they'll learn but more likely the only lesson learned was me re: shopping there.

There are github repositories where people curate a list of domains providing temporary emails or email aliases and admins can just point to the maintained list to block.

In the ~20 I've created so far I've had 2 services that wouldn't accept simple login. For those I've used proton mail's built in email alias service where you get 15 aliases with their proper domain.