The free tools, in one place
A dozen free tools across the DuoCircle family of products. DMARC, SPF, DKIM, BIMI, MTA-STS, an email header analyzer, and a domain authentication audit that runs the lot in one pass. Hosted on the canonical product sites, used by tens of thousands of organizations every month, free with no signup.
Authentication tooling hosted on DMARC Report, the multi-region G2 Category Leader for DMARC software.
DMARC Report Analyzer
Most usefulDrop a DMARC aggregate report (RUA XML or .gz) and see senders, alignment, pass rates, and per-record detail. Parsed entirely in your browser.
DMARC Record Checker
Look up the DMARC record on any domain and see policy, alignment mode, and report destinations.
DMARC Record Generator
Build a syntactically correct DMARC record for any domain. Walks through policy, percentage, and reporting addresses.
DKIM Lookup
Resolve a DKIM selector and inspect the public key and any policy attributes published in DNS.
BIMI Checker
Verify BIMI publication on a domain. Validates the BIMI record, fetches the SVG, and reports VMC presence.
MTA-STS Checker
Check that a domain publishes a valid MTA-STS policy and that the policy is reachable over HTTPS.
Domain Authentication Checker
Run SPF, DKIM, DMARC, BIMI, and MTA-STS in one pass. The full authentication snapshot for a domain.
One-off forensics for the times when a specific message arrived late, looks suspicious, or did not arrive at all. Hosted on Mailflow Monitoring.
SPF tooling hosted on AutoSPF, the SPF management product built because the established vendor would not scale to a $4 per month customer.
SPF Record Lookup
Fetch and pretty-print the SPF record for any domain. Shows includes, redirects, and the resolved sender list.
SPF Checker
Validate that an IP or sender is permitted by a domain SPF record. Shows the include chain that grants or denies.
SPF Validator
Check an SPF record for syntax errors, lookup-count overruns (the 10-DNS-lookup limit), and policy ambiguity.
SPF Record Generator
Build a valid SPF record from your sender list. Flags 10-lookup-limit risks before you publish.
Use them as long as they fit, upgrade when you outgrow the free tier
Every tool above runs on the product site that owns the capability. The DMARC tools live on dmarcreport.com because that is where the paid product runs. The SPF tools live on autospf.com because that is where AutoSPF runs. Use the tools as long as you want, free, no signup. When the free version stops scaling, the paid product is one click away on the same site.
We do not gate the tools, we do not require an email, and we do not store the data you put through them. The DMARC Report Analyzer and Email Header Analyzer in particular parse your data entirely in your browser. Open DevTools and watch the Network tab if you want to verify it.
Need more than the free tier?
Same-day response from someone technical. We tell you yes or no quickly. If yes, we get to work.