You need an existing account, which you can't get if you:
- disable javascript
- don't verify with a phone number
- get stuck in captcha hell
verify with a phone number is notorious for blocking google voice number blocks and detecting devices that aren't pinging cell towers
Plus, as somebody else already said: having JS enabled seems pretty much mandatory if you want to be able to decrypt your emails client-side.
In the EU countries, it has (by law) become very hard to obtain an anonymous prepaid SIM card.
How do you want to decrypt your data client-side without running a software to do just that?
> https://posteo.de/blog/bnetza-entscheidung-zu-posteo-kryptog...
> https://posteo.de/Dienstaufsichtsbeschwerde_Strafanzeige.pdf
(both in German).
https://curia.europa.eu/jcms/upload/docs/application/pdf/201...
Case study: Vincent Canfield, of the half-joke email provider cock.li, moved his servers to Romania after them getting seized by German prosecutors.
https://arstechnica.com/tech-policy/2016/01/cock-li-server-s...
But it should indeed have this kind of response.
Wanting privacy is not a crime.
On the other hand (this is not supposed to be an advertisement or testimonial; I just state the fact), the German email provider Posteo that has some popularity among people who are concerned about privacy also allows anonymous payments via banknotes (cash) that is sent via mail (just put the letter into a postbox in a completely different city).