Under what condition can secret information be sent via USPS express mail?

The condition under which secret information can be sent via USPS express mail is most appropriately described by the principle of considering the effectiveness of the means of communication, which includes security, time, cost, and accountability. This approach aligns with the DoD's emphasis on ensuring that information is transmitted securely and efficiently.

In practice, the decision to use a particular method of communication for transmitting sensitive data is influenced by a thorough evaluation of potential risks and benefits, rather than arbitrary restrictions. When considering USPS express mail, factors such as the urgency of the information, cost implications, and the need for secure delivery channels are all taken into account to ensure that the transmission does not compromise the integrity or confidentiality of the secret information. This complies with established security protocols and best practices for handling sensitive material.

Choosing a method solely based on time of day or specific situations, such as international shipments, does not encompass the broader decision-making process that the Department of Defense requires. Therefore, the correct understanding is that the determination to use USPS express mail must be made based on a comprehensive assessment of the situation considering all relevant aspects.