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MTA-STS Policy Inspector
Parse an MTA-STS policy text and report its version, mode, MX patterns and maximum age.
MTA-STS policy text
mta-sts-policy-inspector.json (complete report and generated source where applicable)
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
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How to use this tool
- Enter values using the displayed examples; observe the documented input shape and limits.
- Choose Calculate result. Review the complete JSON report and any generated source text it contains.
- Download result to save the complete report; copy the generated source member into your project when relevant. Reset restores examples and clears output.
Examples
MTA-STS policy text: version: STSv1
mode: enforce
mx: *.example.com
max_age: 86400
Limitations
- Strict RFC8461 core fields; max_age 0–31,557,600 seconds. No HTTPS retrieval, DNS, certificates or actual mail-host verification.
- Maximum 100,000 UTF-16 units per field, 400,000 UTF-8 combined input bytes, 4 MiB output and 30 seconds in a local worker. Tool-specific bounds may be tighter.
- Generated snippets are source text inside the JSON download. They are never executed by this tool. Local inspection does not verify remote systems or establish standards certification.
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