It's just an email client, acting on the delta chat emails (and moving them to a delta.chat IMAP folder). It works transparently with a fallback that the receiver can still just reply in a normal email client.

It's how the whole messaging drama. Should be resolved and it's using decentralized infrastructure that is already there and reliable.

The default mode of Delta Chats "email interaction" setting is "show only chat messages". This includes replies to messages you sent out from Delta Chat, even if the reply came from another email app or a webmail interface. So you can chat with anyone who you know the email address from.

If you set email interaction to "all" then you see regular email appearing as a "contact request" if you haven't already accepted the sender. In current development repos there is already support for mailing lists, and for html-mail. With this and a few other improvements, delta chat can be used as an e-mail client in more situations.

So it uses the reply chain as identified in the email header.

It might be useful to actually define a new email header field (Or define a new value to put into an existing field), thereby making this an open protocol.

All Delta Chat messages have the "Chat-Version" header. For more specifications see https://github.com/deltachat/deltachat-core-rust/blob/master...