A recipient message system receiving an email message set of two or more email messages and a related condition from a sender to a recipient. The recipient message system detects an attempt from the recipient to read the message set at a second time instance and evaluates the condition at the second time instance. If the evaluation of the condition results in the first evaluation value, the recipient is provided with the first email message in response to the attempt to read the message set, wherein the recipient is not able to read the second email message in this event. If the evaluation of the condition results in the second evaluation value, the recipient is provided with the second email message in response to the attempt to read the message set, wherein the recipient is not able to read the first email message in this event.