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Use Node.js to check whether the MX and TXT records required by an email enrollment flow are visible to your resolver, then compare them with the provider’s current instructions. A matching DNS response confirms only what that resolver returned at check time—it does not prove that a message was delivered, authenticated, or accepted by the enrollment service.
What a Node.js DNS check can verify
Node.js’s promise-based node:dns/promises API can query MX and TXT records. MX results contain a mail server’s priority and exchange hostname; TXT results are arrays of records, with each record represented as an array of character-string chunks. See the Node.js v26.8.2 DNS API documentation for the documented methods and result formats.
A monitor can establish that a particular resolver returned a record matching your expected configuration. It cannot establish that every resolver sees the same data, that mail authentication succeeds, or that a particular service accepted an enrollment. DNS visibility is one part of a larger email setup.
How to check MX records in Node.js
Call resolveMx() with the hostname whose mail routing you intend to check. Replace the example hostname with your domain, and compare the returned exchanges and priorities with the values specified by your mail or enrollment provider.
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import { resolveMx } from 'node:dns/promises';
const hostname = 'example.com';
try {
const records = await resolveMx(hostname);
console.log(records);
} catch (error) {
console.error({ code: error.code, message: error.message });
}Each result has a priority and an exchange. Compare both against the expected configuration: a hostname that appears in the answer with an unexpected priority may still be a mismatch. There is no single MX target that applies to every provider.
How to check TXT records in Node.js
Use resolveTxt() for a TXT record’s owner name. The result is two-dimensional: each inner array corresponds to one TXT record, and its entries are that record’s character-string chunks. Join chunks within a record before comparing a complete value; do not flatten all records together, because that can combine unrelated entries.
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import { resolveTxt } from 'node:dns/promises';
const ownerName = 'example.com';
try {
const records = await resolveTxt(ownerName);
const values = records.map(chunks => chunks.join(''));
console.log(values);
} catch (error) {
console.error({ code: error.code, message: error.message });
}Use the exact owner name and matching rule from the provider’s setup instructions. The domain root may be the right location for SPF, while DKIM commonly uses a selector-specific name and DMARC uses a name under _dmarc. TXT answers can also contain unrelated records; do not assume every returned value is an enrollment token or SPF policy.
Build a monitor that reports useful outcomes
Store the expected record type, owner name, and expected value or matching rule for each domain. For each check, query the relevant record, normalize it according to that record’s semantics, and compare the answer with the expectation. Record when the check ran and the resolver outcome.
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Keep these outcomes separate so an operator can tell what needs attention:
- Match: the expected record or rule was found.
- Mismatch: records were returned, but none matched the expected configuration.
- No matching record: the query completed, but the expected value was absent.
- Resolver error: the query failed; preserve the error code rather than reporting it as a confirmed missing record.
For MX, compare the expected exchange hostnames and priorities. For TXT, join chunks within each record, then apply the provider’s exact comparison rule to the individual records. Avoid broad substring checks when the provider requires an exact token or complete value.
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Polling shows what the monitor’s resolver can currently see. It does not publish DNS changes or guarantee that recursive resolvers and receiving mail servers have the same cached view. The Node.js API documentation does not prescribe a universal polling interval or alert threshold, so choose those based on your operational needs and the provider’s change process.
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What MX and TXT checks mean for SPF, DKIM, and DMARC
These records serve different purposes, and simply finding one does not verify the others:
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- MX: identifies mail exchangers and their priorities for a domain.
- SPF: a TXT record at the sending domain that lists authorized sending systems. Google Workspace advises covering all systems that send for the domain and updating the policy when adding a sender; follow the sending provider’s instructions rather than copying an example blindly. See Google Workspace’s SPF setup guidance.
- DKIM: uses a TXT record commonly published at a selector-specific name. The required selector and value depend on the mail provider.
- DMARC: is published under the
_dmarcname. The applicable standard is described by the current DMARC RFC 9989; the earlier RFC 7489 is also available.
The enrollment provider is not identified here, so there is no universal verification hostname or TXT value to check. Obtain the exact record type, owner name, and value from that provider’s current instructions.
Why a matching DNS response does not prove mail acceptance
Delivery and enrollment can depend on more than record presence, including authentication results, domain alignment, recipient policy, and other message or connection requirements. Google’s email sender guidelines apply to mail sent to personal Gmail accounts, not every recipient service. Google says all senders to those accounts must use SPF or DKIM; senders exceeding 5,000 messages per day must use SPF, DKIM, and DMARC. For direct email at that volume, Google requires the From domain to align with either the SPF domain or DKIM domain.
After a DNS match, test the actual enrollment or mail flow. Where available, inspect the receiving system’s authentication results and the service’s acceptance response. Google’s guidance also identifies valid forward and reverse DNS, TLS, and message formatting among factors relevant to Gmail delivery; a DNS lookup alone does not test those conditions.
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Quick Recap
Practical checklist
- Get the exact record type, owner name, and expected value or matching rule from the enrollment or mail provider.
- Query MX with
resolveMx()and TXT withresolveTxt()fromnode:dns/promises. - Compare MX priorities and exchange hostnames; join TXT chunks per record before applying the expected match rule.
- Report matches, mismatches, absent expected values, and resolver errors as distinct outcomes.
- Record the check time and resolver context, then validate the real enrollment or message flow separately.
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