Bit of a confusing situation here. Officially the address of the watermill is nr 13. But it's only located in the building of 13a.

Currently both are tagged as watermill.

It seems 13a is only used in the official government sources. There's no separate mailbox.

Not a windmill here, some old farm equipment it seems

This structure is not a windmill, but it seems mapping here is also outdated.

This seems to be just a bridge. It's not a watermill since it's lacking a structure where the mill is attached. There's also not multiple channels visible.