Which email service did Yahoo acquire in 1997 for about $92 million?

Yahoo acquired the RocketMail service in 1997 for about $92 million.

The precise corporate detail is that Yahoo acquired Four11 Corporation, the company behind RocketMail. RocketMail was Four11’s free webmail service and one of the first major competitors in the emerging webmail market. Thus, “Yahoo acquired RocketMail” is the standard service-level answer, even though Four11 was the legal acquisition target.

Yahoo absorbed RocketMail’s technology and used it as the foundation for Yahoo! Mail. The transition allowed existing users to keep receiving mail at rocketmail.com addresses, although account and Yahoo ID arrangements changed during the integration.

RocketMail’s history explains why it is sometimes confused with Yahoo Mail: Yahoo Mail was not simply an unrelated service launched from scratch. It inherited much of RocketMail’s webmail system after the Four11 deal. Yahoo later revived the RocketMail domain for new registrations in 2008, but stopped offering new RocketMail addresses in 2013. Existing accounts were treated separately from the option to create new ones.