“All of a sudden we got a huge number of requests for this SMTP gateway.”
Tom Evslin built Exchange at Microsoft, and the reason Gates funded it was fear of Lotus Notes becoming a platform the way Windows was. The internet part was an accident. Customers kept asking for the SMTP gateway that was supposed to be a checkbox feature, and that demand signal was the whole story. Both Microsoft and AT&T got to the internet by chasing a competitor, not by seeing anything coming.