MSN Chat

MSN Chat was the Microsoft Network version of IRCX (Internet Relay Chat extensions by Microsoft), which replaced Microsoft Chat, a set of Exchange-based IRCX servers first available in the Microsoft Comic Chat client, although Comic Chat was not required to connect.

According to the MSN Chat website, the following were required to use the MSN Chat Service:

The Microsoft Network Chat Control was developed as an ActiveX Component Object Model (COM) Object. ActiveX, being a Microsoft technology provided limited compatibility for other products. The other major platforms beside Internet Explorer that MSN Chat was supported on, was Netscape Navigator and MSNTV (formerly known as WebTV). To ensure the MSN Chat network was only being connected to by authorized clients, Microsoft created and implemented a SASL based Security Service Provider authentication package known as GateKeeper. This used a randomized session key to authorize users not using the Microsoft Passport (now Microsoft account) system. Microsoft used another SSP known as GateKeeperPassport, that worked from the same method but required certain attributes related to the user's account.

There have been various methods through the use of mIRC to access the MSN Chat Network. Most of the methods were through the use of the MSN Chat Control itself, yet others were more complicated.

...
Wikipedia