European parcel delivery firms and postal systems (Deutsche Post DHL, La Poste, Royal Mail, PostNL and all the non-legacy competitors) generally do not commission purpose-built vehicles, they buy off the shelf small vans and light commercial vehicles.
* of course I do know why, "because jobs and politics"...
In comparison, polish postal system although it's pretty much standard european approach:
- postal trucks deliver mail between post offices
- in cities and more built-up rural areas, on-foot postman delivers mail from post office
- in very sparse rural areas or for households far from village center, mailboxes are placed in centralized location and you have to go to pick up them on your own.
Mail pickup is done from dedicated sending boxes usually on outside of post offices, sometimes one might be placed further away in rural areas. No curb-side pickup.
Such differences mean that normal cargo vehicles can be easily used between post offices, and even for rural areas you arrive, park once, handle unloading, and drive again, instead of constantly starting and stopping to access road-side mailboxes.