https://fml.srht.site (or equivalently https://securemail.srht.site)
Hosted on SourceHut open-source platform!
Private by Design. No data collection. No registration. Zero ads/tracking. Completely free. Anonymous. No Javascript. Privacy-conscious staff.
End-to-end encryption for secure conversations. Independently maintained. Simple, easy to use, and available on all platforms. No downloads required.