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Kitterman SPF Validator vs MXToolbox: catalog facts
Kitterman SPF Validator	MXToolbox
Free Free to use.	Freemium Lookups on the site are free to use, with paid plans offered alongside.
Web	Web
Uses an RFC 7208 compliant library Tests processing limits such as DNS lookup count	Many email and DNS checks in one place MX lookups query the authoritative server directly
Cached DNS results can lag recent changes Plain interface aimed at technical users	Pages carry prompts for the paid service Each check runs separately rather than as one combined report
Web application	Web application
Closed source	Closed source
License not stated	License not stated
No account needed	No account needed
Needs internet	Needs internet
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.