1. A computer-implemented method for detecting undesired email containing image-based messages, the method comprising the steps of: (i) issuing, at an email security device, appropriate tokens and token values for each of a pre-selected set of text-related characteristics of an email under consideration; (ii) issuing, at said email security device, appropriate tokens and token values for each of a pre-selected set of image-related characteristics of an image in the email under consideration, at least one token associated with an image-related characteristic being dependent upon a result of image processing analysis on data comprising the image; (iii) performing, at said email security device, a statistical analysis of the tokens associated with text-related and image-related characteristics issued for the email under consideration and determining a probability that the email is undesired; and (iv) employing, at said email security device, the determined probability to decide whether the email is undesired.