With advances in information and communication technologies (ICT), organizations of various forms now deploy an increasing number of ICT-enabled persuasive systems in several domains. Traditional computer-mediated communication (CMC) theories mainly focus on the effectiveness of media in the synchronous/asynchronous spectrum for effectively matching medium with communication task. The contemporary communication environment is rich with asynchronous channels such as email, Web, and text messaging, which makes it important to go beyond synchronicity and determine the nuances among various asynchronous channels. No rigorous research has compared the effectiveness of these channels in the persuasive systems domain where organizations use technology to persuade users to modify their behavior in a direction that they mutually agree to be desirable. In this paper, we study the effectiveness of CMC and the strategy used to frame the persuasive message. We explore persuasive strategies of praising, reminding, suggesting, and rewarding for health behavior and promotion. We model user experience as a mediator between channel strategy combinations and persuasive effectiveness. Through controlled user studies, we compared sixteen combinations of communication channel and persuasive strategy with or without emoticons. We found that channel/strategy combinations affect persuasive effectiveness (mediated by user experience) in varying degrees. Our findings contribute to the body of CMC and persuasive system knowledge and have practical implications for online advertising, health promotion, and persuasive technology design.