A system and method of detecting undesired email containing image-based messages employs a statistical analysis process which identifies and assigns probability values to the presence of each of a pre-selected set of text-related characteristics of an email under consideration and to the presence of each of a pre-selected set of image-related characteristics of the email under consideration. The identified characteristics and their associated probability values are used to determine whether the email is undesired. In one embodiment, the identification and assignment of probability values is a Bayesian analysis and, preferably, a Statistical Token Analysis. The system and method can identify undesired emails which contain images having messages, generally in the form of text in the image.