A communication server supports automatic content receipt and distribution. The communication server receives a set of content objects, where a content object of the set is associated with a set of target group identifiers. A content object of the set may include different versions of content for ABn and/or multivariate testing. The communication server generates target segment identifier combinations and distributes versions of messages proportionally to each user identifier associated with the target segment combinations. The server generates engagement metrics corresponding to interaction by the user identifiers with the messages. The metrics may be generated for each message version, each group of users, and each group combination.