Letter box in front door - never seen one, doesn't mean they don't exist.
Box near the road - yes, there are many post boxes attached to front walls, fences, houses etc. We have a box near to the front door which can be seen easily from the road. The postman never uses it, he prefers to come to the back of the house and either leave the post on a patio table or, if he's in a rush and therefore doesn't actually stop and get of his motorbike, it gets chucked in the direction of the table.
Some people, especially those who live some distance from the main village, collect their post from the kafenio.
Most houses appear to have numbers but not all. In the first apartment I lived in we had no house number, to try to help the postie we included in our address "next to KEP", it seemed to work, well 80% of the time!