Concluding the Arc Experiment
The ARC experiment aimed to address issues with DMARC authentication failures caused by intermediaries modifying email messages. When messages are forwarded, authentication can break due to changes in IP addresses and message content, leading to legitimate emails being flagged as unauthenticated. The experiment sought to create a signature chain that allows trustworthy intermediaries to attest to the original state of the message before any modifications occurred.
- ▪DMARC relies on SPF and DKIM authentication, which can fail when intermediaries modify messages.
- ▪Forwarding often breaks authentication because the forwarding infrastructure appears as the sending IP.
- ▪The ARC experiment targeted the issue of intermediaries rewriting messages and aimed to establish a chain of custody for email authentication.
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Record
| Original publisher | Ietf |
| Canonical URL | https://www.ietf.org/archive/id/draft-adams-arc-experiment-conclusion-00.html |
| Publication time | Tue, 19 May 2026 21:23:25 +0000 |
| Retrieval time | 2026-05-19T21:34:58.272Z |
| Last seen | 2026-05-19T21:34:58.272Z |
| Headline source | Publisher (no WeSearch rewrite) |
| Excerpt source | publisher body |
| Excerpt method | First ~120 words (~800 chars) of extracted publisher body, fair-use limited. |
| Summary | WeSearch · cerebras-chat (WeSearch summarizer) |
| Summary source text | contentText |
| Citation coverage | Summary is a WeSearch-generated derivative; primary citation is the original publisher URL. |
| Cluster | PHZaewi0aScf |
| Cluster logic | Grouped by semantic title/content similarity across sources within a rolling window. Same-publisher template collisions are excluded from coverage comparison. |
| Ranking reason | Story pages are not engagement-ranked. Hub feeds use recency, with optional source-diversified chronological ordering (cap consecutive stories per source). No personalized ranking. |
| Publisher visit | Yes — open original |
| Substitutes article? | No — link-out required for full text |
Rights status (four layers)
WeSearch handling by dimension
| Indexing | May the item be indexed (stored, ranked, made findable)? | Allowed |
| Snippet | May a short excerpt of the publisher's text be shown? | Allowed |
| AI summary | May WeSearch generate its own short summary of the article? | Limited |
| Retrieval / RAG | May the content be exposed for third-party retrieval-augmented generation? | Not asserted |
| Model training | May the content be used to train AI models? | Not asserted |
| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
2.1. Problem Space: DMARC Breakage at Intermediaries DMARC relies on successful SPF and/or DKIM authentication along with alignment with the Author Domain. When intermediaries modify a message (for example, subject or body changes, footer insertion, MIME adjustments), DKIM signatures from the originator can fail to verify; when an intermediary relays mail through different IPs than are defined within the originator’s SPF record, SPF authentication can fail. As a result, messages that were legitimate at origination can appear unauthenticated downstream, even if the intermediary handling is benign.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Ietf.
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