How can you effectively gather targeted email lists for marketing campaigns?

Neil Patel suggests identifying online communities relevant to your business, such as specialized groups or Yelp listings, and gathering email addresses from these sources. He recommends using services like Mechanical Turk where you can pay workers (approximately three cents per hundred emails) to compile targeted email lists. Once collected, these lists enable mass email marketing campaigns promoting products as valuable upselling opportunities for businesses. Patel shares a real example where this strategy generated over half a million dollars in sales over 12 months for a cleaning business, demonstrating its effectiveness for targeted email marketing.