The first thing that users must remember is that as long as a parcel is being shipped Priority Mail delivery confirmation is always FREE. This applies to regular Priority Mail and the Flat Rate Boxes and Envelopes. If you are shipping via Parcel Post, Media Mail and First Class Mail, delivery confirmation is an extra 14 cents, so you must make sure that this extra cost is included in your overall shipping cost that you charge your customers. You can opt out of the delivery confirmation, but then your customers will not have any notification if their package is on the way, just your word.