The overwhelming consensus is that B2B lead vendors' claims of opt-in leads are generally unreliable and should be approached with strong skepticism. Experts, marketers, and documentation sources highlight numerous risks associated with purchased lists, including low data quality, poor engagement, negative impacts on sender reputation and deliverability, potential legal violations (CAN-SPAM, GDPR), and damage to brand reputation. It is strongly recommended to verify lead data, focus on inbound marketing strategies, build email lists organically through permission-based methods, and carefully assess lead vendors before believing their claims. Prioritizing genuine consent and clean data is crucial for effective and compliant email marketing.