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.
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 really like this idea
> 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.