What this analysis does
Enter a domain to retrieve its current MX routes, priorities and likely inbound provider. Mailybox also recognizes the standards-defined Null MX signal for domains that intentionally reject mail and explains when SMTP may fall back to an A or AAAA address because no explicit MX exists.
How to use the result
Use real evidence
Paste the exact domain, header, message or configuration. The result is only as useful as the evidence supplied.
Review the findings
Mailybox separates observations from inferred causes so you can see what is known and what still needs verification.
Retest after changes
Email authentication and routing are stateful. Re-run the analysis after publishing a fix.
Interpretation matters
Email systems combine DNS, message-level evidence, provider policy and intermediate infrastructure. A single passing check is not proof that every message will deliver, and a single warning is not proof that a domain is misconfigured. Mailybox is designed to expose the evidence and the relationship between signals so the next action is clear.