Ask HN: Where do those LLM-generated outreach emails come from?

I have started getting daily LLM-written outreach emails. They all follow the same exact pattern, but come from different people pitching different vibe-coded things. The authors are real people with LinkedIn profiles, usually AI gurus, rarely experts in their niche. The message is usually targeted compliment > pitch > call to action. The compliment is the biggest tell because it's so neat and specific.

My question: which tool are they all using? Why has it become so popular almost overnight? How do I reliably block those emails?