Certified mail is an add-on service offered by USPS for First Class mail that provides proof of mailing to the sender. With electronic USPS tracking, the sender is notified when the mailing was delivered or that a delivery attempt was made. An Electronic Return Receipt showing the recipient's signature is also available.
You send letters as Certified mail through the Lob API by passing the value certified in the “extra_service” parameter of the create letter request. You may similarly opt for an Electronic Return Receipt by passing certified_return_receipt in the “extra_service” parameter.
Please note that both the Certified Mail and Electronic Return Receipts add-on features will each receive an additional charge that is independent of one another. Both the Certified mail and the Electronic Return Receipt add-ons are only available for First Class mail sent domestically within the US. To see the incremental cost of sending Certified mail through Lob, please refer to our pricing page.