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MXToolbox's SuperTool, the gold standard for email deliverability diagnostics. You can run SPF lookups, DKIM checks, DMARC validation, MX record checks, blacklist queries, and more, all from one interface. Free for the core checks every marketer or developer needs.
How to use it
Open SuperTool and find the unified search bar at the top.
Type your domain and pick the check you want from the dropdown. SPF, DKIM, DMARC, blacklist, MX lookup.
Submit and wait a few seconds for the diagnostic to run.
Review the results. Green checks mean the record is set correctly. Red flags need fixing.
Click into any flagged issue for the specific record value and recommended fix.
After implementing fixes in your DNS, rerun the check to confirm everything passes.
Best-fit use cases
DNS record QA
Validate SPF, DKIM, and DMARC every time you change email providers or add a new sender.
Blacklist monitoring
Confirm your domain or IP is not on any major spam blacklist before a big campaign.
New domain audits
Check the email-related DNS records of any new domain before connecting it to your sender platform.
Deliverability incident response
Diagnose deliverability drops with structured checks across every standard authentication layer.