Deliverability & inbox testing

Email Forwarding Tester

Analyse a forwarded email's headers to confirm the forwarding path and detect whether it broke SPF — and whether SRS or ARC protect it. Free, in your browser.

Test email forwarding

Paste the full raw headers of a forwarded message ("Show original" / "View source").

What this forwarding tester does

Confirms whether a message was forwarded
Detects the forwarding method (Resent, Delivered-To, ARC)
Checks whether forwarding broke SPF
Detects SRS return-path rewriting
Detects ARC preservation of auth results
Explains how to keep forwarded mail authenticated

Common use cases

  1. 1Diagnosing why forwarded mail fails DMARC
  2. 2Confirming a forwarding rule is working
  3. 3Checking if your forwarder uses SRS
  4. 4Investigating lost or bounced forwards
  5. 5Verifying ARC is applied by a mailing list
  6. 6Auditing an email routing/forwarding setup

Related tools

Email Header AnalyzerEmail Routing AnalyzerARC Record CheckerSPF Record CheckerDMARC Record CheckerEmail Authentication Analyzer

About email forwarding

Forwarding breaks SPF: when a message is relayed by a forwarder, the sending IP no longer matches the original domain’s SPF record, so SPF fails at the final destination. Two mechanisms fix this — SRS (Sender Rewriting Scheme) rewrites the return-path so SPF passes for the forwarder, and ARC (Authenticated Received Chain) preserves the original authentication results so the receiver can trust them.

This tool reads a forwarded message’s headers to confirm it was forwarded, identify how, and tell you whether SRS or ARC are in place. If SPF failed and neither is present, forwarded mail may be filtered — enable ARC/SRS at the forwarder, and lean on DKIM, which survives forwarding intact.

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FREQUENTLY ASKED QUESTIONS

Got Questions? We Have Answers.

What does the forwarding tester check?

It reads a forwarded message's headers to confirm it was forwarded, identify how (Resent headers, Delivered-To mismatch, ARC), and report whether SPF broke and whether SRS or ARC are present to mitigate it.

Why does forwarding break SPF?

When a forwarder relays a message, the sending IP no longer matches the original domain's SPF record, so SPF fails at the final destination unless SRS rewrites the return-path.

What are SRS and ARC?

SRS (Sender Rewriting Scheme) rewrites the return-path so SPF passes for the forwarder. ARC (Authenticated Received Chain) preserves the original authentication results so the receiver can still trust them.

How do I get the headers?

Open the forwarded message and use "Show original" in Gmail or "View source" in Outlook, then paste the full raw headers.

Does DKIM survive forwarding?

Usually yes — DKIM signs the message content, which forwarders typically leave intact, so DKIM often still passes where SPF fails. That is why DKIM plus ARC is the reliable path for forwarded mail.

Is my pasted email uploaded?

No. The headers are parsed entirely in your browser and never leave your device.