New York Times - secure means of providing a news tip

The New York Times has suggestions for persons who would like to anonymously forward news tips to the Times - at this link. [1]  Of course, the suggested methods - using sites which encrypt and do not store identity back-track information - can be used for communication to other news organizations or persons.   

It is significant that the Times is providing the information - what are they aware of which is not public?    Just the recommendation to put your tip mail into a post box, and not take it into the post office is significant.    Why use a post box?   There are video cameras running in all the post offices.   

Another suggestion the NYTimes provides is to use a public wi-fi connection:   "We strongly recommend that tips be sent using a public Wi-Fi network, and that the computer you use is free of malware. If the computer is compromised,

communications using SecureDrop may be compromised as well. The steps below outline best practices for use of SecureDrop, as well as the steps that we take to protect your privacy."