Advertising mail, also known as direct mail, junk mail, or admail, is the delivery of advertising material to recipients of postal mail. The delivery of advertising mail forms a large and growing service for many postal services, and direct-mail marketing forms a significant portion of the direct marketing industry. Some organizations attempt to help people opt out of receiving advertising mail, in many cases motivated by a concern over its negative environmental impact. Advertising mail includes advertising circulars, catalogs, CDs, pre-approved credit card applications, and other commercial merchandising materials delivered to both homes and businesses. It may be addressed to pre-selected individuals, or unaddressed and delivered on a neighbourhood-by-neighbourhood basis