ARC (Authenticated Received Chain) is a framework designed to improve email authentication and deliverability by preserving email authentication results across multiple hops, especially in cases where emails are forwarded or passed through intermediaries (e.g., mailing lists or email forwarding services). It ensures that the original authentication results (like SPF, DKIM, and DMARC) are not lost during email forwarding, which can otherwise lead to legitimate emails being marked as spam. Learn more: https://en.wikipedia.org/wiki/ARC