IRCX
IRCx was a set of extensions to the IRC protocol used by several Microsoft implementations of IRC.
On the server side, IRCX incorported a number of unique featurs, including channel properties/metadata, multilingual support, UTF-8 nicknames and channel names (represented as hexadecimal to legacy clients), and tiered channel permission levels (owner, host, voice).
IRCX was originally implemented in Microsoft Exchange 5.5 to replace the propriatary Microsoft Chat, and was also available in Microsoft Exchange 2000. A third party IRCD called TESX also implements the IRCx protocol but is likewise abandoned.
On the client end, IRCx was implemented within the much-maligned and now discontinued Microsoft Comic Chat, which was included with Internet Explorer 3, 4, and 5.