Thanks all for the great discussion here. We compiled what we can answer into this new FAQ:

https://confluence-public.open-xchange.com/display/CoiW/FAQ

>90% of mails are delivered really in a couple of seconds, but yeah, turnaround could be quicker. That's why in the longer run we hope to skip the store-and-forward mechanism and instead deliver mails directly by IMAP server to IMAP server.

That's one client we are working on. That client uses delta.chat core to which we are also contributing.

That's great, I'm really excited about your project.

We are working on server specs, the idea is that certain functionality like WebPush, WebRTC calls, channels require the servers to support COI.

Do you know, is it going to have a demo/beta server just to play it.

The specs will soon be available on GitHub soon. If the server supports JMAP, there are no principle obstacles to also support COI over JMAP. But as said, currently the market share of JMAP is neglible.

i assume for this to work remotely ok the imap idle is a must. also how is it supposed to work on the receiving site ? There has to be some "Folder" where those messages are stored and the imap idle should listen to that folder or else my inbox will be huge mess and mess with my regular mail client.

also was there any tests how long does it take for delivery, because the message could hop around and could be scanned, added addotional headers or mess with those there.

You can also run your own mail servers, even non-technical people could do that with for example https://thehelm.com/. Haven't tried it out myself, though.

Which solves nothing if the other party's email is provided by Google. Google is still getting your chats.

XMPP and Matrix other people can host their servers on Google as well.

Fundamentally, if you don't trust the decisions of the person you are talking with, you can't guarantee the privacy of your chats.

You're forgetting E2E encryption.

Delta.chat supports E2E with other Delta users and Autocrypt email clients, so the point stands.

Very true, but have you tried just reaching out to someone via email on Matrix in practice? I tried with Riot and am not able to do that. Maybe just a bug, but if you want the real Matrix experience, you need a Matrix account. Don't get me wrong, I do love Matrix, but I also love XMPP - both not spectacular successes so far. AFAIK, the French Matrix version is even locked down and does not federate across the network.

You can reach out to folks by email in Riot by hitting "start chat" and entering an email address. I'm not sure how much easier we can make that ;)

We should run a general purpose email bridge though, and in fact there's a massive public sector outfit asking for such a thing currently so it'll probably happen sooner than later.

In terms of Matrix not being a spectacular success - well, that's a matter of perspective. The intention for France is absolutely for it to federate with the public network (once there's are sufficient border gateways in place). And France is far from the only high profile Matrix deployment out there, it's just one that we can speak about. But eitherway, COI looks cool, and I hope it helps OX sell more mail servers :)