Waltham, Mass.—IMN, a Web-based newsletter provider, announced Monday it has added podcasting to its e-mail newsletters. Marketers will be able to add preproduced podcasts to e-mail newsletters and track audience behavior. Podcasts include any audio content, which readers can play either through their computers, on Apple’s iTunes or by downloading the audio file to portable players, such as iPods. IMN is using the new feature in the October 2005 issue of “Informed Marketer News,” its own e-mail newsletter. In a literal case of “the medium is the message,” it features a podcast about the benefits of podcasting.