I think they meant boxes that you use to send post (the red thing with the slot for the letter) as opposed for receiving boxes, which are those tiny lockers you open with a key to get your incoming letters.
Those usually exist in the post offices themselves, or in small dedicated buildings. It’s usually done in areas where there are no delivery directly to your own box in your own building, such as villages/Moshavs, or certain low-density neighborhoods. Here’s an example from Yahud: https://goo.gl/maps/5U2EMoCQSo42
If you move west on the streetview you can see this building also has the red outgoing mail box, but it’s not really a post office, since it’s not staffed.
The regulations about these are listed here:
https://www.israelpost.co.il/madrich.nsf/ItemsTree/91DB97EA836720D342256CF9002AEBC2?opendocument
Since these are also used by the public, I think it makes sense to map them - if you move somewhere new and don’t know exactly where these boxes are located, the map could help you find it.