IN EVERY COUNTRY OF THIS WORLD IT IS ILLEGAL. Don’t be dumb guys.
You either violate competitive or unsolicited contact laws. Only because you get away with what you are doing as an individual (for the time being), does not make it legal. You can also scam people online or sell drugs and get away with. If I would run a client management company and I get one of your stupid emails I would sue you to death, just because you are competitor (if you are local).
A way to work around that I having proxy companies that sell those leads to you, but those setups are expensive and need a stupid nominee to get their head killed once shit hits the fan. And even after that there are still risks involved.