USPS regulations (https://pe.usps.com/text/dmm300/508.htm) Section 1.8.2 and 1.8.3 require that the recipient of any mail received must have a notarized 1583 form on file.
If you receive mail from a recipient who does not have a 1583 form on file, we suggest calling the customer and notifying them of the situation.
We ask that you keep the mail item for at least 24 hours before returning it to the post office.
To resolve this issue, customers can log in to their portal and click on the blue Complete Verification button.
They will then be prompted to follow the instructions and have their documents notarized online for a faster transaction.