Oregon Certificate of Mailing (6Â N) is a form used by individuals or businesses in the state of Oregon to request evidence of mailing from the United States Postal Service (USPS). It is used to obtain proof of mailing for packages, letters, or other items sent through the USPS. This certificate of mailing is typically used for legal purposes and provides a record of when the item was sent, and to whom. It also provides a record of the delivery status of the item. There are two different types of Oregon Certificate of Mailing (6Â N):6Â NN-1 an6Â N6N-IN6Â NN 6N-1 is for items sent domestically within the United States, while 6Â N-2 is for items sent internationally.