The answer is yes, Certified Mail® can be sent to a P.O. Box. You simply address the letter to a P.O. Box instead of a street address.
If the Certified Mail letter requires a signature from the recipient, the mail carrier will leave a delivery slip (PS Form 3849) inside the P.O. Box instructing the recipient to present the delivery slip to the window clerk.
The window clerk will hand over the Certified Mail letter after the recipient signs the USPS Green Card, which is returned to the sender via First-Class Mail, or signs on an electronic pad which results in an Return Receipt (Electronic) being generated by the USPS and made available to the mailer as a PDF file.
Mailers who use SimpleCertifiedMail.com® to prepare their outbound Certified Mail receive the Return Receipt (Electronic) in their account within 24 hours of the window clerk collecting the recipient’s signature. The RR(E) is the legal equivalent to the old-fashioned PS 3800 Green Card. Receiving this PDF file within 24 hours helps mailers move legal and business processes ahead much faster than waiting for signed Green Cards to come back via First-Class Mail. It’s also much easier to store the PDF electronically in a client file than to store Green Cards in a file cabinet.