Will All of my mailing pieces be delivered? Quite frankly, No. Direct mail is a very effective method of marketing a product or service, and the mailing list is a very important part of the campaign. However, mailing lists cannot by guaranteed 100%. The plain truth is people move, people die, calamities like fires or floods happen, and disrupt the delivery chain. All things aside, look for a mailing list that is guaranteed to be at least 95% deliverable. This is an industry standard with most b2b (business) and consumer marketing mailing lists. True residential saturation mailing lists will be almost 100% deliverable.