When mail drops through the letterbox, what’s printed on the envelope can matter just as much as what’s inside. Advertisers understand that eye-catching claims and graphics can give consumers that added incentive to tear a letter open and read its contents. But it’s important for consumers to recognise what they’re reading as a piece of advertising, and letters that shock or mislead them because of what’s printed on the envelope run the risk breaking a number of advertising rules. This Advertising Guidance explains the rules that apply to marketing claims on the outside of direct mail envelopes, and the types of claims and graphics to avoid.