1. A method for invite enforcement in an online service environment, the method comprising: at one or more computing devices comprising one or more processors and storage media storing one or more computer programs executed by the one or more processors to perform the method, performing operations comprising: storing, in a database, an association between a team of one or more user accounts and a domain name service domain; receiving a request to invite a user at an e-mail address to join the team, the e-mail address belonging to the domain name service domain; creating, in a database, a placeholder user account that is a member of the team; associating, in a database, the e-mail address with the placeholder user account; and after an invitation for the e-mail address to join the team is accepted, converting, in a database, the individual user account to a team account that is (a) a member of the team and (b) associated with the e-mail address.