http://www.codinghorror.com/blog/archives/001081.html

You may remember Sierra's ImagiNation network from the earliest days of dial-up networking:

The ImagiNation Network (INN), aka The Sierra Network (TSN), was the first online multiplayer gaming system. Developed by Sierra On-Line in 1989, and first available to the public in 1991, the ImagiNation Network was a unique online gaming network that gave subscribers from all over the United States of America a place where they could "play games, make friends and have fun". With a wide variety of games including RPGs, WWI aeroplane simulations, live trivia, and card and board games, almost every user could find something enjoyable to play. INN also featured an electronic post office, many bulletin boards, chat rooms, and the company boasted of having "more than 200 groups, clubs and special events online."