To determine the sender of certified mail being held at the post office, look at the top right corner of the orange notification slip. The sender's name is typically filled in by the post office prior to delivery of the certified letter.
Certified mail is a service provided by the post office to track receipt of mail. For an extra fee, the sender can ensure that the letter is delivered because the recipient must sign for delivery. The sender receives proof that the recipient actually took possession of the mail.
If the sender's name is not included on the orange slip, call the post office directly. Be ready to provide the tracking number shown on the orange notification slip.