• Microsoft Exchange Server

    Block attachments with htm or html extensions and/or javascripts in Office365

    Spammers have been getting craftier with how they get through the bayesian and other heuristic filters many mail providers use to deliver only legitimate emails to recipients. One of the ways they do this is by encoding or encapsulating patterns into base64 or some other encoding mechanism. This allows the email client to render a message with text that would have been blocked by a spam filter as the filter usually can’t comprehend the encoded strings. These usually come down in the form of htm or html attachments where the email client effectively acts as a web viewer to render data to the screen. If we take a sample of…