Your mail was refused
“After delivery, an addressee may mark a mailpiece “Refused” and return it within a reasonable time, if the piece or any attachment is not opened.” — USPS DMM 508 §1.1.3
I’ve been in the habit lately of refusing all my junk mail. I certainly don’t want to pay for removing the trash I get in the mail. Why not make the sender pay for it? (Undeliverable first class mail will get returned to the sender, while undeliverable presorted standard mail (which is most junk mail) will get disposed of by the USPS. That’s just a part of the service that a mailer is buying when paying postage.)