Techniques for invite enforcement. In one embodiment, for example, a method comprises: receiving an acceptance of an invitation to join a team of one or more team user accounts held with the online service; based on receiving the acceptance and based on determining that an owned domain name service domain of an owned electronic mail address is associated with the team, offering a personal user account an option between at least: (a) converting the personal user account to a team user account that is a member of the team, and (b) changing an electronic mail address associated with the personal user account from the owned electronic mail address to one that has a different domain name service domain than the owned domain name service domain associated with the team.