portchecker.me

Email diagnostics

Inspect MX, SPF and DMARC for the supplied domain and optionally the DKIM key for a known selector. Each result includes observed records and interpretation limits.

Use the s= value from the DKIM-Signature header of a sent message. Without a selector, DKIM is not queried.

No messages are sent and no mailboxes are tested. Queries are not stored. DNS uses Google Public DNS; HTTPS checks originate from our server.

How to interpret and act

Start with MX: confirm targets and priorities in your email provider’s dashboard. Null MX may be correct for a domain that accepts no mail; absent MX also requires investigating the A/AAAA fallback. Compare SPF and DKIM with the values supplied by your actual sending service. Change one setting at a time, retain previous values and recheck after the TTL.

Limitations

This is a record inspection, not a complete deliverability assessment. DMARC is queried only at _dmarc for the supplied name; inherited policies and DNS tree discovery are not evaluated. SPF is not executed for a sender/IP and includes are not expanded. DKIM does not prove that messages are signed. No result guarantees inbox delivery.

Technical sources

RFC 7208 · RFC 6376 · RFC 7505 · RFC 9989

Continue troubleshooting

DNS lookup · SSL/TLS checker · HTTP header inspector · Domain check-up