Compare the MX values in your mail provider’s current setup instructions with the records at the domain’s active DNS host, the answers from each authoritative nameserver, and answers from recursive resolvers. If authoritative answers are correct but a recursive resolver still returns an older or empty result, caching is plausible. If authoritative answers are wrong or inconsistent, fix the DNS configuration rather than waiting.
What counts as the correct MX record?
There is no universal MX target or priority. Use the mail provider’s current custom-domain setup instructions or admin panel as the baseline, including any directions about existing records. Providers can change their setup requirements, and Google Workspace notes that older accounts may use different MX values from current setups. Do not rely on an old guide or copy another provider’s values.
Compare the full set of required hostnames and priorities—not just whether an MX record exists. Also check for obsolete entries: Microsoft advises removing old MX records or assigning them lower precedence than the Microsoft 365 record. In MX priority, the lower numerical value is preferred.
Check the DNS zone that actually serves the domain
The registrar and DNS host may be different companies. First identify the nameservers delegated for your domain; then inspect the zone at the provider operating those nameservers. A change made in a registrar’s DNS screen will not affect public answers if another service hosts the active zone.
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In the active zone, compare the MX owner/name field, target hostname, and priority with the provider’s current requirements. Check for typos, truncated or outdated targets, a misplaced name field, missing priority, and old provider records. Confirm that the mail provider is checking the intended domain and setup state.
Compare configured, authoritative, and recursive answers
Use these checks in order. Cloudflare’s email troubleshooting guidance gives dig example.com mx +short as a way to query MX records and recommends comparing results with the DNS records page and the provider’s instructions. Replace example.com with your domain. If dig is unavailable, use an available nslookup implementation or a DNS lookup service; command syntax varies by platform.
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- Read the active DNS zone. Confirm the configured MX records match the provider’s required targets and priorities.
- Query each authoritative nameserver. Ask each delegated authoritative server for the domain’s MX records. These answers show what the domain’s DNS service is publishing.
- Query one or more recursive resolvers. Compare each result with the authoritative answers. Check returned targets, priorities, and TTLs where available.
- Use the differences to choose a next step. If authoritative answers are correct but a recursive answer is old or empty, caching is plausible. If authoritative answers are wrong, differ across nameservers, or do not match the provider’s requirements, investigate the zone, publication, or delegation.
| Comparison | What it tells you | If it does not match |
|---|---|---|
| DNS zone vs. provider instructions | Whether the configured values appear to be the intended ones | Correct the name, target, priority, or obsolete entries. |
| Each authoritative nameserver vs. DNS zone | What the authoritative service publishes | Check that you edited the active host, that the zone was published, and that delegation and authoritative servers are consistent. |
| Recursive resolver vs. authoritative answer | Whether that resolver currently returns data consistent with the authority | Check TTLs and negative caching; compare another resolver. |
| MX lookup vs. test mail | Whether DNS advertises the expected route versus whether mail actually flows | If MX is correct, investigate provider verification, mailbox readiness, routing, and the specific error or bounce. |
A TTL is a clue to how long cached data may remain, not proof that the record is correct. Different recursive resolvers can show different answers because their cache histories differ. RFC 8767 also describes resolver behavior that can serve stale DNS data for resilience, so an expired TTL does not guarantee every resolver immediately stops returning an older answer.
Allow for positive and negative caching
A resolver may cache an old MX answer until its cached data expires. It may also cache a negative answer—such as a response indicating that MX data was absent. Adding the record afterward does not necessarily replace that cached absence immediately. RFC 2308 specifies that the negative-answer TTL is derived from the lower of the SOA record’s TTL and SOA MINIMUM value.
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Microsoft’s domain-record troubleshooting guidance says a new record is typically visible to Microsoft within a few minutes, though it can occasionally take a few hours. That is Microsoft-specific guidance, not a universal DNS deadline. The useful evidence is the state of authoritative and recursive answers, their TTLs, and the provider’s verification result—not a blanket promise that DNS always takes 24–48 hours.
Decide whether to wait or correct the record
- Wait and recheck: the active zone is configured correctly, authoritative nameservers return the intended MX set, and one or more recursive resolvers still return older or empty data. Retry verification after the relevant cached data has had time to expire.
- Correct the DNS setup: authoritative answers contain the wrong target or priority, omit a required record, include conflicting old MX entries, or differ across authoritative servers. Verify the active DNS host and zone publication before changing records again.
- Escalate the mail problem separately: authoritative and recursive MX answers match the provider’s expected values, but provider verification or delivery still fails. Check mailbox readiness, routing, provider-side setup, and the exact bounce or error. Microsoft documents a separate mail-flow validation process for Exchange Online connector issues.
Recognize unusual or misleading records
If a lookup shows records you do not recognize, do not assume they are the intended mail route or delete them without checking their purpose. Cloudflare’s troubleshooting page specifically flags unexpected _dc-mx or dc-##### subdomains and directs readers to its Unexpected DNS records guidance.
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An MX lookup confirms what DNS advertises; by itself, it does not prove that the recipient mailbox exists or that every mail-routing component works. Treat DNS verification and end-to-end mail testing as separate checks.
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