We have a similar mode of operation, with traditional scam-like marketing, where a hand-scrawled 'note' is placed in mailbox, or on front door:
"We replaced the windows, for your neighbor, 'Karen', and noted some aging on your house...".
That gets things on a less stranger and more like (your neighbor) used our product, and recommends for you.
Leaving little notes, maybe not outlawed, but still in same spirit, as the unwanted email thing;
Likely a 'shrug and ignore' level of concern.
Hint: (You need to always take into account the country and local conditions, comparatively, for crimes, on the seriousness scale.)