I went down a brief rabbit hole on the zip+4 and the IMb (intelligent mailer barcode). The +4 was originally a local division inside a single zipcode, like a neighborhood or mail route. +4 and the barcode was then called POSTNET -- decommissioned and now upgraded barcode encoding to IMb, which can contain like 2000 bits of data. The zip +4 technically now has a length of 11 digits, and is inside a IMb barcode.

Conclusion, barcodes have sensitive data too. ~✍️

edit add: i wanted to see if my phone's barcode app could scan too see if OP's post office really calls him Mr. Off, but it cant natively read mailer codes and I fell asleep and the rabbit hole ended.