If I interpret the homepage correctly clients/servers without extra COI enhancements will just receive the messages as emails. Not ideal, but in any client with threading (gmail, apple), it would work decently i guess.

According to the spec (https://confluence-public.open-xchange.com/display/CoiW/COI+...) clients are expected to ask the IMAP server using a CAPABILITY command whether it supports COI extensions. Whether or not the server does support COI, messages are indeed standard mails with an extra Chat-Version: header and the requirement that Message-Ids start with "coi$".

So an existing server need not do anything to support COI clients. But a malicious server could easily decide to reject them, or to filter out COI-specific stuff from messages. I don't think it's likely, but it sometimes big corporations and governments get paranoid about weird things ("network load!!1!") and take technical measures to block them.

I wouldn't be surprised if COI encounters issues with automated abuse detection and spam filters in those servers. When you're in an active conversation, the client is rapidly sending 1-line emails with strange headers.

> likely to implement a protocol like this into their own servers?

just on the homepage "Since this is all based on email, you can communicate with users even when they do not have COI-compatible servers or apps."

the likely side effect is that you'd need to filter out chats messages into a folder or something to reduce the inbox clutter

I've browsed through the spec and it looks like servers likely won't need to change anything. Most of the interaction between clients happens via mail headers.

I really like this idea

The service works as a layer on top of standard email. There will be optional IMAP extensions to reduce the overhead.

Google already has IMAP. I don't know about the other two, but I would be surprised if they don't.

Are server-side changes needed?

> The COI ecosystem is the COI Standard plus compatible Client Apps and Email Servers.

> COI works with all email severs, but IMAP servers can be enhanced with extra COI capability.

I’d take this to mean that no, changes are not explicitly required; but without the changes COI functions the same as email, but in an IM interface.

They have a description of the client but I could not find a description of the optional server-side enhancements (besides that it should be advertised via CAPABILITY).

Chat over IMAP seem a bit misleading title. Their proposition is to add additional info in MIME headers. Or later some of them like Message-Id with chat info. So seem more related to MIME and SMTP. A client app can get those headers with different protocols too. MAPI, EWS, JMAP, etc.

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.

Chat over SMTP/IMAP/MIME just doesn't sound right, or does it? We also thought of Chat over Email, or Chat over Mail, But Chat over IMAP gave us the COI (fish), which we love. Decision made :)

Chat over Email is so much clearer as a name.