DNS failure

When the address domain does not exist

Verification looks up the address domain and its mail route in DNS. The cause of a failed lookup determines how to read status, action and reason_codes.

DNS_NXDOMAIN for the address domain establishes that the name does not exist. Emvero can return undeliverable with reject without contacting a mail server. NXDOMAIN for a target reached through an alias is a routing problem; it does not establish that the original domain is missing. RFC 2308 defines NXDOMAIN.

When the lookup cannot be completed

DNS_SERVFAIL records a failed lookup, DNS_TIMEOUT records a lookup that exceeded its time limit, and DNS_DNSSEC_FAILURE records failed validation of signed DNS data. These conditions leave the domain’s ability to receive mail unresolved. Emvero returns unknown with allow_with_email_confirmation.

A later lookup may succeed. Sending SMTP clients also defer and retry after temporary DNS errors under RFC 5321. A lookup that could not finish does not supply a missing-domain answer.

When the requested records are absent

DNS_NODATA means the name exists but has no records of the requested type, as defined in RFC 2308. For example, if example.com has no MX record, SMTP may use its A or AAAA address as an implicit route. Emvero checks that possibility. An empty MX answer neither settles delivery nor guarantees that the API returns the NODATA code. The MX record explanation covers this fallback.

A contradictory route can produce DOMAIN_MAIL_ROUTE_MISCONFIGURED. That route, and a route with no usable destination, remain unresolved. An explicit null MX declares that the domain accepts no mail. The guide to domains without MX records explains these cases.

Read checks.mail_routing alongside the status and reasons. The email domain checker inspects domain evidence, without establishing whether an individual mailbox exists.