1. In a computing system, a method of operation comprising: identifying a message adaptation specification for adapting a base electronic message; identifying, based at least in part upon the message adaptation specification, one or more digital content elements to supplement the base electronic message, each of the one or more digital content elements selected from a corresponding plurality of differently versioned digital content element candidates; and adapting the base electronic message to include the identified one or more digital content elements to form an adapted electronic message.