← Glossary
Authentication
What is ARC (Authenticated Received Chain)?
A way for intermediaries such as mailing lists and forwarders to preserve the original authentication results.
How it works in practice
Forwarding often breaks SPF and a mailing list that edits the message breaks DKIM, so a legitimate message can fail DMARC on arrival. ARC lets each hop record what it saw so the final receiver can decide whether to trust it. Gmail and Microsoft use it, and you'll see ARC headers when you read the headers of forwarded mail.
The common mistake
Treating an ARC-Authentication-Results header as the authentication verdict of the message itself.
Check it yourself
Related terms
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