Very cool! Which client did you write?

I had forgotten they tried to standardize the protocol!

Yeah, it was surprisingly easy. Connect to the switchboard server, set up sessions from there, and then it's all MIME. We even implemented avatars for Gaim by chunking Base64-encoded images over MIME messages (they had a max length), which MSN would ignore but Gaim would use.

We never had any trouble from the MSN team. Rumor had it at the time that at least one dev on the team was secretly a Gaim user, and they just looked the other way.