A server system hosts a plurality of conversations, each having an identified set of participants. For a respective conversation, the server provides content of the conversation to the participants of the conversation. The server receives content from each of a plurality of participants of the conversation and transmits the received content to the other participants of the plurality of participants. Upon an additional participant being added to the conversation, the server provides content of the conversation to the additional participant that includes all content provided to the identified set of participants, and adds the additional participant to the identified set of participants.