What is the purpose of a return address on an envelope?

The primary purpose of a return address on an envelope is to identify the sender in case the mail cannot be delivered. This allows postal services to return the item to the original sender if there are issues with the recipient's address, such as it being incorrect or if the recipient has moved. The return address ensures that the sender can be located, thus facilitating the retrieval of undelivered mail.

In contrast, charging extra fees for delivery is not related to the purpose of a return address. While tracking the delivery route of the mail is important, it generally involves other postal services or tracking numbers rather than the return address itself. Lastly, while additional information might be useful for the recipient, it is not the primary function of the return address, which focuses specifically on identifying the sender for potential return.