A system for automatically preparing customized replies in response to communications from a plurality of clients. To facilitate automation and tracking, each original communication to the client (or each original response from the client) is tagged with a unique label, and replies to client responses are each correspondingly labeled. The system provides individualized replies to each of a variety of response options that a client might exercise in response to a received communication, whether an original communication or a reply to a previous response. The system is applicable to mass marketing communications, and is particularly well suited to the generation of personalized replies to each and every one of a multitude (tens of thousands and up to millions) of communications from clients. The system is also capable of continuing to generate replies to follow-up responses from clients and to thereby maintain an ongoing "conversation" until the client makes a purchase decision, or no longer responds. Communications may be delivered through a variety of means, such as the internet, the mails, by facsimile, on a host communication, etc.