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/spf-checker
SPF Checker
Validate a domain's SPF record for email sender authorization.
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About SPF Checker
SPF Checker looks up a domain's SPF record and shows exactly which mail servers it authorizes to send on its behalf, along with the raw record so you can read the includes and the final policy yourself.
Run this when setting up a new mail provider to confirm the record was added correctly, when email is unexpectedly landing in spam, or as part of a wider check into how well a domain is protected against being spoofed.
A domain with no SPF record at all leaves every recipient's mail server with nothing to check incoming mail against, which this tool flags directly rather than treating as a lesser concern.
Tutorials
SPF Records ExplainedHow a domain publishes which servers are allowed to send email on its behalf, and how to read the syntax of a real SPF record.6 min readWhy Email Spoofing Still Works Without SPF and DMARCWhy the openness of the original email protocol makes forgery possible by default, and exactly what each authentication check does and does not stop.6 min readSPF, DKIM and DMARC: How the Three Actually Fit TogetherThree separate email authentication mechanisms that only work as a system, and why checking just one of them tells an incomplete story.6 min read