While door drops are powerful because they're measurable, their main advantage is still that they compel people to take action, says Sonia Hitzelberger, Account Development Director at door drops specialist Whistl. The beauty of door drops today is how measurable they are - we've seen great advancements with regards to data and targeting models. As recently as 10 years ago, clients were sending door drops without being able to prove how effective they could be. It's fine to send out a great item, with great offers and great impact, but if you're not evaluating correctly then you're not using door drops to their full potential.