Which packaging technique is required for anonymous mail?

The required packaging technique for anonymous mail is to isolate and leave it separate from other packages. This approach is crucial for maintaining the confidentiality and privacy associated with anonymous mailings. By isolating the package, postal services can minimize the risk of it being mixed with other mail that might have identifiable information, thus protecting the anonymity of the sender.

Maintaining this separation is essential for security measures, ensuring that the delivery process does not compromise the sender's intent. The other options do not appropriately support the anonymity requirement; for instance, labeling with the sender’s name would directly contradict the concept of anonymous mail, and using standard boxes or regular envelopes may not adequately address the specific handling needs of such mail.