WOT: Hotmail mail servers

[user list]

I have just heard a rumor that the hoemail mail servers are not MS exchange 
servers but, rather, linux mail servers. Is this true? If so, is this well 
known? we are fighting a guerrilla action over this where I work. I'm on a unix 
server that never has problems while the rest of the institution runs on 
exchange servers that are about as reliable as power in California.