What are the two features of anonymous mail?

The correct choice highlights that anonymous mail typically weighs over 13 oz and bears only stamps. This aligns with the guidelines for sending anonymous mail, as it allows for a certain level of confidentiality and discourages personal identification of the sender.

Mail that weighs over 13 oz must be sent using specific services, often making it necessary to handle it with care to maintain anonymity. The requirement that it bears only stamps means that there cannot be any return address or identifying information associated with the sender, which is critical for maintaining anonymity.

This understanding of weight and postage type is essential in postal operations, where adherence to weight restrictions and proper use of postage is necessary to ensure correct handling and delivery. The other options present misleading or incorrect facts about the requirements for anonymous mail, including incorrect weight limits and packaging needs.