ARC (Authenticated Received Chain)
A set of headers that preserve an authenticated chain of custody across intermediaries such as forwarders and mailing lists, so a later receiver can see what the authentication result was before the message was handled.
In plain terms
A way for forwarders to vouch for what a message looked like when they got it.
Why it matters for deliverability
Forwarding and mailing lists routinely break SPF and sometimes DKIM. ARC gives the final receiver a way to see that the message authenticated correctly earlier in its journey, instead of judging it only on the last hop.
What to do about it
- If you run a forwarder or list, seal messages with ARC.
- If you are chasing DMARC failures for legitimate mail, check whether forwarding is involved before changing policy.
- Do not expect ARC to rescue mail that never authenticated in the first place.
Source
RFC 8617 — The Authenticated Received Chain (ARC) Protocol
“provides an authenticated "chain of custody" for a message, allowing each entity that handles the message to see what entities handled it before”
Checked 2026-08-29
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Definitions reviewed 2026-08-29. Spotted something wrong? Tell us.
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