https://delta.chat/en/help#e2ee
I gave it another try last week
- the onboarding automatically creates a username/password on the server you selected, more details here: https://chaos.social/@delta/115479392746850836
- E2EE using openpgp
- fast and light on resources
It’s still in development, it’s not a fully fledged replacement for Matrix yet, but I could see it replace Signal at some point.
For a list of servers: https://chatmail.at/relays


Years (and years) ago, I used it for a while. I kept getting locked out of my email (GMX) account. The messages DeltaChat creates are obviously full of cyphertext, and to a spam filter they look very spammy.
The DeltaChat concept is an interesting idea, and clearly a sort of progress, but it’s also a bit of a hack. As a stopgap solution, fine, but I say the day we can replace Signal is the day that Matrix becomes usable. I wish that day would come sooner.
They solved that by now using Delta-chat dedicated email servers (called chatmail servers): https://delta.chat/en/2023-12-13-chatmail
Definitely much better that what it used to be, I had a similar experience to you a few years ago.