Mail configuration check

Runs the MX, SPF and DMARC checks together and checks DKIM for any selectors you supply. DKIM is only checked for given selectors; a missing selector is not proof of missing DKIM.

Updated 2026-10-07

What this tool checks

The mail configuration check runs the MX, SPF and DMARC checks together and returns one report. If you give selectors in a single check, it adds a DKIM record check for each of them, up to five.

Each part behaves as on its own tool page: SPF check, DMARC check, DKIM record check and MX lookup.

Bulk checks

The API runs the MX, SPF and DMARC parts on up to 20 domains in one request.

The bulk check does not take DKIM selectors, so it does not run DKIM. The results keep the order of the input, and duplicates count as items. An item that fails for a technical reason is reported as an error for that item and does not fail the other items. Read bulk checks for the request format.

How to read the result

The report gives an overall status and the findings of each part. If any part could not be completed, the status is unknown, and the findings tell you which part.

Limitations

DKIM is checked only for the selectors you supply. A missing selector is not proof of missing DKIM.
The check reads DNS only. It does not test delivery or connect to mail servers.

Use it from code

API reference for Mail configuration check · bulk API reference

curl -i "https://api.probekit.dev/v1/mail/check?domain=example.com"

curl -i -X POST https://api.probekit.dev/v1/mail/check/bulk \
  -H 'content-type: application/json' \
  -d '{"domains": ["example.com", "example.org"]}'

A request without payment is answered with 402 Payment Required and the exact price. See the API reference.

Bulk

Check several domains in one request. Each item costs $0.024, with a minimum charge of $0.03 per request and at most 20 domains.

Domains	Price
1	$0.03
5	$0.12
10	$0.24
20	$0.48

Limits

Input	Domain, DKIM selectors (optional)
Deadline	10 seconds
Freshness	Up to 5 minutes, never longer than the record TTL
Price	$0.03 per check, $0.024 per item in bulk (minimum $0.03)

Findings this tool can report

Check (3)

Warning CHECK_DEADLINE_EXCEEDED The check did not finish within its time limit.
Warning CHECK_INTERNAL_ERROR The check failed because of an internal error.
Warning CHECK_QUERY_BUDGET_EXCEEDED The check stopped after reaching its DNS query limit.

DKIM (7)

Error DKIM_INVALID_KEY The DKIM public key is not valid base64.
Warning DKIM_KEY_REVOKED The DKIM key for this selector is revoked (empty p tag).
Error DKIM_MULTIPLE_RECORDS More than one DKIM record was found for the selector.
Warning DKIM_NOT_FOUND No DKIM key was found for the given selector.
Error DKIM_SYNTAX_ERROR The DKIM record contains a tag that cannot be parsed or has an invalid value.
Info DKIM_TESTING_MODE The DKIM record is in testing mode (t=y).
Warning DKIM_WEAK_KEY The RSA key is shorter than 1024 bits.

DMARC (10)

Info DMARC_INHERITED The DMARC policy comes from the organisational domain.
Error DMARC_INVALID_POLICY The DMARC record has a missing or invalid p tag.
Error DMARC_MULTIPLE_RECORDS More than one DMARC record was found.
Warning DMARC_NOT_FOUND No DMARC record was found for the domain or its organisational domain.
Info DMARC_NO_RUA The DMARC record has no aggregate report address (rua).
Info DMARC_PARTIAL_PCT The DMARC policy applies to only part of the failing mail (pct below 100).
Info DMARC_POLICY_NONE The DMARC policy is p=none (monitoring only).
Error DMARC_SYNTAX_ERROR The DMARC record contains a tag that cannot be parsed or has an invalid value.
Info DMARC_UNKNOWN_TAG The DMARC record contains tags that are not defined.
Info DMARC_UNSUPPORTED_REPORT_URI A DMARC report address uses a scheme other than mailto.

DNS (3)

Error DNS_DOMAIN_NOT_FOUND The DNS resolver reported that the domain does not exist.
Warning DNS_RESOLVER_FAILURE The DNS resolver returned a server failure.
Warning DNS_RESOLVER_TIMEOUT The DNS resolver did not answer in time.

MX (5)

Warning MX_NOT_FOUND The domain has no MX records.
Info MX_NULL The domain publishes a null MX and does not accept mail.
Error MX_NULL_WITH_OTHERS A null MX is published together with other MX records.
Error MX_TARGET_IS_IP An MX record points to an IP address instead of a host name.
Error MX_TARGET_UNRESOLVABLE An MX host has no A or AAAA records.

SPF (13)

Error SPF_INCLUDE_LOOP The SPF chain returns to a domain it already evaluated.
Error SPF_INCLUDE_NOT_FOUND An included or redirected domain has no SPF record.
Info SPF_MACRO_NOT_EVALUATED An SPF record contains macros that were not evaluated.
Error SPF_MULTIPLE_RECORDS More than one SPF record was found for a name in the SPF chain.
Warning SPF_NEUTRAL_ALL The SPF policy ends with ?all.
Warning SPF_NOT_FOUND No SPF record was found for the domain.
Warning SPF_NO_ALL The SPF record has no all mechanism and no redirect.
Error SPF_PASS_ALL The SPF policy ends with +all.
Warning SPF_PTR_MECHANISM An SPF record uses the ptr mechanism.
Info SPF_SOFTFAIL_ALL The SPF policy ends with softfail (~all).
Error SPF_SYNTAX_ERROR An SPF record contains a term that cannot be parsed.
Error SPF_TOO_MANY_LOOKUPS The SPF record needs more than 10 DNS lookups.
Error SPF_TOO_MANY_VOID_LOOKUPS More than two SPF lookups returned no data.

Frequently asked questions

Why is the status unknown?

If any part of the check could not be completed, for example because of a resolver timeout, the overall status is unknown instead of a guess based on the parts that did finish. The findings say which part was incomplete. Running the check again usually helps.

Why is DKIM missing from the report?

DKIM is only checked for selectors you supply, up to 5. A domain can use any number of selectors, so the check never reports 'no DKIM' on its own.

How many domains can I check in bulk?

Up to 20 domains per request. Results come back in the order you sent them, and a duplicate counts as an item.

What does a bulk check cost?

The price is $0.024 per domain, with a minimum of $0.03 per request. A single mail check costs $0.03. See the pricing page.