http://www.usps.com/ncsc/addressservices/addressqualityservices/confirm.htm

Confirm is a service available from the United States Postal Service that uses the PLANET™ barcode to electronically track First-Class Mail®, Periodicals, and Standard Mail™ letters and flats.

There are two types of Confirm service that let you know where your mail is, and when it will be delivered. Both provide you advance notice of when your mail pieces will arrive.

• Destination Confirm service (for outgoing mail) gives you advance information about when your mail pieces will reach their destinations.
• Origin Confirm service (for incoming mail) lets you anticipate when customers' checks, replies, or orders are on the way back to you.

Before you start using Confirm service to track mail pieces, you decide what information you need:

• If you use Confirm service to track outgoing mail (Destination Confirm service), you can use PLANET Codes to identify different attributes you wish to track.
• If you use Confirm service to track incoming mail (Origin Confirm service), you can use PLANET Codes to identify the mail sender.

Each mail piece should contain a POSTNET™ and a PLANET barcode. The Postal Service™ sorting equipment reads both barcodes and makes them available to a centralized network server. The mailer then receives data electronically and learns when outgoing mail is nearing delivery or when reply mail is on its way to you.