SixDegrees.com is a social network service website that initially lasted from 1997 to 2000 and was based on the model of social networking. It was named after the six degrees of separation concept and allowed users to list friends, family members and acquaintances both on the site and externally; external contacts were invited to join the site. People who confirmed a relationship with an existing user but did not go on to register with the site continued to receive occasional email updates and solicitations. Users could send messages and post bulletin board items to people in their first, second, and third degrees, and see their connection to any other user on the site.