The Authenticated Received Chain (ARC) is a standard created in 2016 to improve how DKIM and SPF results are passed from one mail server to the next during forwarding. When messages are forwarded through intermediaries like mailing lists or email account forwarding, DKIM and SPF can break, causing authentication failures. ARC aims to fix this by preserving email authentication results across subsequent intermediaries ("hops") that may modify the message. This allows receivers to trust the authentication results and deliver legitimate messages from indirect mailflows. While ARC is implemented by email receivers and ISPs, customers like Postmark can use it to improve DMARC reports with less failures resulting from forwarding. The standard includes headers such as ARC-Authentication-Results, ARC-Seal, and ARC-Message-Signature that allow the ARC chain to be validated during each hop.