Free, at least what isn't covered by other tiers, sells you. Credit card... definitely not anon. Were it zclassic, zcash, bitcoin, etc, and/or cash in mail, they and others might have something there. Don'f forget, people happily pay $3/mo just for stable, corp, independant, email. Add in some sort of crypto enforced privacy and it's sweeter value add. Even without that, any community of service choices independant from the big three dataminers and govt lovers, is better odds than nothing. Either way, validate the crypto / smtp marketing first if that sort of privacy is required. If it still uses smtp on the backend, or is serving you code to execute on the fly, it's probably not as resistant or novel as need be. As said many times before, Email ecosystem as we know it is broken and unfixable, don't even try, you need to outright replace it with something entirely new. Go p2p, or distributed, or at least zk.