The October 2020 false Spamhaus listing, caused by a new feature generating false positives, highlights the critical importance of robust Quality Assurance (QA) within blocklist operations. These lists, like Spamhaus, aim to combat spam and cyber threats using verifiable criteria. However, even temporary listings can significantly impact email deliverability and sender reputation. Therefore, continuous monitoring of IP and domain reputation, maintaining open communication with blocklist providers, and actively participating in feedback loops are essential. Addressing issues, demonstrating compliance, and understanding delisting procedures are also crucial. Blocklist operators should enhance QA by incorporating real-world data and sender feedback, emphasizing transparency and accountability as standard practice.