The present invention relates to the processing of E-mail messages over a telecommunications network. More particularly, the present invention relates to the detection and monitoring of file formats which can be processed and displayed at an E-mail client. Specific embodiments include, sending an E-mail message to the E-mail client, determining at the E-mail client a file format that the E-mail client can process and display, and indicating to the E-mail sensor server the file format that the E-mail client can process and display. Once the file format is determined, subsequent E-mail messages maybe of the same file format. The file format could be hyper text mark up language (HTML) statements or dynamic HTML(DHTML) statements or Java applets. The method may also include monitoring the status of the E-mail message received at the E-mail client.