Across various sources, including email marketing experts, technical documentation (RFCs, CAN-SPAM), and real-world platform recommendations, the consensus is that relying solely on the 'From' address in mailto: unsubscribe requests is unreliable and a poor practice. Key issues include the potential for email spoofing, forwarding of emails to different recipients, and the existence of tagged/receive-only addresses. Modern best practices emphasize using web-based unsubscribe links with unique identifiers, one-click unsubscribe options (RFC 8058), and clear/accessible preference centers. Compliance with regulations (CAN-SPAM) and proactive list management (cleaning, re-engagement) are also vital.