It's fine as a throwaway email. Unfortunately it's such a pain to register anonymously since the conditions have to be just right, it's a lottery. Try and move on to something else if it doesn't work.
IMO people who are obsessing over email providers are compensating for their lack of good OPSEC. You should never delegate your OPSEC to your email provider, assume they will stab you in the back. The essential question is just if you can use it in such a way to soften their backstabbing, e.g. can you register and use it anonymously over Tor.