By default, MailWasher only displays in plain text. HTML can carry viruses and other scripts which can run when viewed. Although HTML is easier to read and better to look at, it is potentially harmful to view HTML email if you are unsure of the sender. MailWasher does allow an option to view HTML emails by clicking the 'View HTML' button in the preivew pane, or setting it so that Friends emails are always in HTML (Settings>>Display>>Inbox>>Disable sticky HTML preview)