Defaults.Exposed › October 2026 census › v10 registry › Reverse DNS (PTR)
Reverse DNS (PTR)
Methodology v10 · canonical ID reverse-dns · Email Security · scored
Helps your mail server look legitimate so messages aren't junked.
Reverse DNS (PTR): definition
| Canonical ID | reverse-dns |
|---|---|
| Category | Email Security |
| Grade impact | Scored, counts toward the grade |
| Pass | The domain's mail-relevant IP (Internet Protocol) has a PTR (Pointer, reverse DNS) record. |
| Fail | No PTR record exists for the address. |
| Example (passing) | 10.0.113.203.in-addr.arpa. PTR mail.example.com. |
Reverse DNS (PTR) across the census
77.2% of domains with a mail-relevant address have a PTR (reverse DNS) record (139,217,449 of 180,346,153, as of October 12, 2026).
Aggregates only: never an individual domain's result.
How this check is scored
Reverse DNS (Domain Name System, PTR) is one of the 24 scored checks in methodology v10. It carries points toward the grade, and a pass earns them. When the result cannot be determined for a domain (a timeout, a SERVFAIL, a redacted source), the check returns N/A and drops out of that domain's scoring denominator. A result that could not be determined is never counted as a fail; a determined absence is.
In the October 2026 census, 152,146,166 of the 332,492,319 graded domains had no determinable result for this check: the check needs a mail host to look up, so it runs only on domains with MX (Mail Exchange) records whose primary mail host resolves.
Every outcome in the census
| Outcome | Domains | Share of domains with a mail-relevant address | In the headline figure |
|---|---|---|---|
| Mail host address has a PTR record | 139,217,449 | 77.2% | Yes |
| No PTR record | 41,128,704 | 22.8% | No |
Source: the October 2026 census rollup, deduplicated per domain, as of October 12, 2026.
By top-level domain
This splits the share of domains with a mail-relevant address that have a PTR (reverse DNS) record by TLD, with generic and country-code TLDs kept apart. A TLD is named below only when at least 100,000 of its domains are in this check's base.
| Kind | Combined share | Highest | Lowest |
|---|---|---|---|
| Generic TLDs (gTLDs): 353 TLDs, 117,344,303 domains | 73.9% | .dev 92.1%, .studio 91.2%, .app 87.9% | .xyz 7.18%, .asia 62.6%, .site 64.8% |
| Country-code TLDs (ccTLDs): 167 TLDs, 62,672,244 domains | 83.3% | .ee 95.6%, .hu 95.1%, .hr 94.0% | .cn 23.0%, .br 59.4%, .kr 61.6% |
The largest TLD in this base, .com, stands at 77.6% (63,998,150 of 82,509,024).
Kind follows the IANA (Internet Assigned Numbers Authority) delegation type: every two-letter TLD is a ccTLD. The per-TLD rollup covers 180,016,547 of the 180,346,153 domains in this base. Grade shares for every TLD are on TLDs compared: the census section.
Against the other checks
Among the 7 Email Security checks with a published figure, Reverse DNS (PTR) has the 1st highest pass share. Next below it is MX records: 54.3% of graded domains. Across every check with a published figure it ranks 8th of 24 .
Each share is measured on the check's own base, named on its page, so the ranking compares rates across different sets of domains.
Fix it
Plain-English impact, cost of ignoring it, and step-by-step remediation: How to fix Reverse DNS
Cite this check
Defaults.Exposed, "Reverse DNS (PTR) (reverse-dns)", Grading Methodology v10 (census as of October 12, 2026). https://defaults.exposed/methodology/reverse-dns
Permalink: https://defaults.exposed/methodology/reverse-dns ·
All 33 checks: v10 registry ·
Machine-readable: /methodology/checks.json ·
Licence: open data