Developer Reference

Reverse MX Lookup (Deprecated)

Explore Reverse MX Lookup (Deprecated) API documentation, request parameters, response fields, code examples, and error handling for DomScan integrations.

Reverse MX Lookup (Deprecated)

Deprecated: this endpoint performs exact-hostname searches only against a best-effort seven-day index populated by prior /v1/dns/all lookups. Each MX host keeps at most 10,000 recent entries. The API evaluates limit entries before returning one row per apex by default, and it is not an internet-wide dataset.

GET /v1/reverse/mx

Query Parameters

Parameter	Type	Description
mx required	string	Exact mail server hostname to check in the deprecated DomScan passive cache (alias: mailserver; e.g., "aspmx.l.google.com")
match optional	string	Matching mode. Only exact is supported.
include_apex_only optional	boolean	When true (default), return one row per apex domain. Set false to preserve observed hostnames.
limit optional	number	Maximum recent index entries to evaluate before optional apex deduplication. Default: 100, max: 1000.

Use Cases

Check cached DomScan observations for an MX host
Review prior API lookup context for mail infrastructure
Confirm whether DomScan has seen matching domains before
Use as a limited legacy signal, not a full dataset

Example Request

# Deprecated limited cache lookup for prior DomScan DNS observations
curl -H "X-API-Key: your-api-key" "https://domscan.net/v1/reverse/mx?mx=aspmx.l.google.com&limit=100"

# Deprecated limited cache lookup for another MX hostname
curl -H "X-API-Key: your-api-key" "https://domscan.net/v1/reverse/mx?mx=outlook.protection.outlook.com"

Example Response

{
  "query": {
    "mx": "aspmx.l.google.com",
    "match": "exact",
    "include_apex_only": true
  },
  "deprecated": true,
  "deprecation_notice": "This endpoint is deprecated. It only searches a best-effort seven-day passive index populated by prior /v1/dns/all lookups and capped at 10,000 recent entries per key. It is not an internet-wide reverse DNS dataset.",
  "results": [],
  "summary": {
    "total_found": 0,
    "returned": 0
  },
  "freshness_summary": {
    "source": "passive_dns",
    "cache_status": "passive_cache_only",
    "result_count": 0,
    "returned_count": 0,
    "apex_domain_count": 0,
    "apex_deduped_count": 0,
    "warnings": ["passive_cache_only", "no_cached_matches"]
  },
  "page": {
    "limit": 100,
    "next_cursor": null
  },
  "meta": {
    "source": "passive_dns",
    "note": "Best-effort seven-day index populated only by prior /v1/dns/all lookups"
  }
}

Response Fields

Field	Type
`query`	object
`query.mx`	string
`query.match`	string
`query.include_apex_only`	boolean
`deprecated`	boolean
`deprecation_notice`	string
`results[]`	object[]
`results[]`	object
`results[].domain`	string
`results[].apex`	string
`results[].mx`	string
`results[].all_mx[]`	object[]
`results[].all_mx[]`	object
`results[].all_mx[].host`	string
`results[].all_mx[].priority`	integer \| null
`results[].last_seen`	string \| null
`results[].reason`	object
`results[].reason.type`	string
`results[].reason.matched`	string
`summary`	object
`summary.total_found`	integer
`summary.returned`	integer
`freshness_summary`	object
`freshness_summary.source`	string
`freshness_summary.cache_status`	string
`freshness_summary.result_count`	integer
`freshness_summary.returned_count`	integer
`freshness_summary.apex_domain_count`	integer
`freshness_summary.apex_deduped_count`	integer
`freshness_summary.warning_count`	integer
`freshness_summary.warnings[]`	string[]
`freshness_summary.last_seen_span_days`	integer \| null
`page`	object
`page.limit`	integer
`page.next_cursor`	string \| null
`meta`	object
`meta.generated_at`	string
`meta.source`	string
`meta.query_time_ms`	integer
`meta.note`	string
`cache`	object
`cache.hit`	boolean \| null
`cache.age_s`	integer \| null
`cache.ttl_s`	integer \| null
`cache.key`	string \| null