Gmail and Yahoo will start enforcing new bulk sending requirements in February 2024, targeting senders of over 5,000 emails per day. These updates aim to reduce user spam, emphasizing sender responsibility for brand integrity and user protection. The guidelines include a one-click unsubscribe mechanism, which must be implemented by using specific headers and handling POST requests to return a blank page with a 200 or 202 status code. Additionally, Gmail and Yahoo now require DMARC alongside SPF and DKIM for email security and authenticity, with a focus on improving list management and monitoring spam complaints. Senders are advised to track spam rates under 0.3% and implement one-click unsubscribe functionality to maintain email integrity and trust.