What must be done with accountable mail upon delivery to the addressee?

For accountable mail, it is essential to have the addressee sign off on the receipt upon delivery. This process serves as proof that the delivery has taken place and that the mail was received by the correct individual. The signature signifies that the addressee acknowledges receipt of the mail, which is crucial for tracking and accountability purposes.

Documenting delivery in a logbook, while important in certain contexts, does not replace the necessity of the signature, as the signature on the receipt is the key evidence of delivery. Discarding receipts is not appropriate since they are vital for record-keeping. Returning the mail to the sender does not apply in scenarios where the mail is successfully delivered to the intended recipient. Therefore, having the addressee sign off on the receipt is the correct and critical step in handling accountable mail.