Fwiw Protonmail still has free accounts (500MB storage limit). They used to accept Bitcoin too, and their FAQ says they do, but I don't see the payment option.

A workaround however, would be to use an anonymous credit card. This way recurring payments are also possible (as long as BOLT12 doesn't have broad support)

The Bitcoin Company offers anonymous online Visa cards, but I'm sure there's others too: https://thebitcoincompany.com/