What does "preference" mean?

The priority order a sending mail server tries hosts in — lower numbers first. Two hosts with the same preference are tried in any order; a higher number is a backup, used only if the lower-preference hosts don’t answer.

Why is there no MX list for this domain?

Either the domain publishes no MX records, or it declares a null MX (RFC 7505 — "this domain accepts no mail," on purpose, common for a domain that only serves web traffic). Both cases read the same on this page: no mail exchangers to list.

Can I paste an email address instead of a domain?

Yes. Paste the whole address and the domain is used automatically — the page shows when it has done this.

Does this check whether a specific inbox exists?

No. It resolves the domain’s mail servers only. Whether a given mailbox at that domain accepts mail is a separate question this gate does not answer — no message is sent and no mail server is contacted.

Does it check SPF, DKIM or DMARC?

No. Those are separate DNS record types (TXT) this check does not query. This page is MX records only.

Do you keep the domain I typed?

No. The request is processed in memory and dropped; nothing is written to a database, storage or logs.

FREE TOOL

MX lookup

Enter a domain and see its MX records — every mail server DNS lists for it, in the order mail delivery tries them, over one DNS-over-HTTPS MX query. Paste a whole email address instead and the domain is used automatically. It does not tell you whether a specific mailbox exists at that domain — no message is sent and no mail server is contacted — and it does not check SPF, DKIM or DMARC records.

INPUT

Domain

try

200 OK115 ms (api)

CLEAN

No findings

5 checks run

5 mail servers

Pref	Host
10	aspmx.l.google.com
20	alt1.aspmx.l.google.com
20	alt2.aspmx.l.google.com
30	aspmx2.googlemail.com
30	aspmx3.googlemail.com

{
  "ok": true,
  "verdict": "clean",
  "findings": [],
  "data": {
    "dns": {
      "nameservers": [
        "ns-1087.awsdns-07.org",
        "ns-1882.awsdns-43.co.uk",
        "ns-423.awsdns-52.com",
        "ns-705.awsdns-24.net"
      ],
      "resolves": true
    },
    "mx": [
      {
        "host": "aspmx.l.google.com",
        "preference": 10
      },
      {
        "host": "alt1.aspmx.l.google.com",
        "preference": 20
      },
      {
        "host": "alt2.aspmx.l.google.com",
        "preference": 20
      },
      {
        "host": "aspmx2.googlemail.com",
        "preference": 30
      },
      {
        "host": "aspmx3.googlemail.com",
        "preference": 30
      }
    ],
    "rdap": {
      "ageDays": 11339,
      "createdAt": "1995-09-12T04:00:00.000Z"
    }
  },
  "checks_run": [
    "domain.dns",
    "domain.mx",
    "domain.parked",
    "domain.rdap",
    "domain.typosquat"
  ],
  "checks_skipped": [],
  "meta": {
    "gate": "domains",
    "ms": 115,
    "ruleset": "reference-a39927da"
  }
}

The full /v1/domains gate also checks

Domain resolvesParked domainRegistration ageLook-alike domain

Also available through the API.

Join the waitlist /v1/domains docs

Live call to the same /v1 endpoint customers use. Rules only on this page; nothing you type is stored.

What it checks

domain.mx — one DNS-over-HTTPS MX query for the domain. On a real answer, every record surfaces as data.mx[] (host, preference), sorted so the first entry is what a sending server tries first. This check emits no finding either way — a domain without MX isn't a problem for /v1/domains, only data. data.mx is absent, never an empty array, when there is nothing to list: no MX records, a null MX (RFC 7505), or the domain not existing.

The rest of /v1/domains runs on the same call: DNS presence, RDAP registration age, parking, typosquat. See the domain age checker.

What the result means

MX records present — the domain has working mail exchangers; read the list for the hosts and their order. The verdict on this page comes from the other four checks (a parked or newly registered domain can still have MX records), not from having MX records — this is the one gate on the site where "MX records exist" is not itself a finding.

No MX records — either the domain publishes none, or it declares an RFC 7505 null MX. Both read the same here: no mail exchangers to list, so the domain can't receive mail either way.

Why it matters

A domain with no MX record or a null MX cannot receive mail, full stop — no signup confirmation, no password reset, no invoice will ever arrive. That is visible from the DNS record alone, before any mail is sent and before a bounce comes back. Seeing the actual hosts and their preference order is also how you confirm a mail-server migration went through, or that a provider's setup instructions (which host, which priority) were followed correctly.

From your own code

curl -s -X POST https://api.stormdoor.dev/v1/domains \ -H "Authorization: Bearer sk_live_..." \ -H "content-type: application/json" \ -d '{"domain":"stripe.com"}'

Read data.mx[].host and data.mx[].preference. The API needs an account — signups open with paid plans, a one-time trial included, no card. Join the waitlist and you will hear first.

MX lookup

What it checks

What the result means

Why it matters

MX records,
answered.

From your own code

Read more

Guides about this

MX lookup

What it checks

What the result means

Why it matters

MX records,answered.

From your own code

Read more

Guides about this

MX records,
answered.