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dig

dig

CLI DNS lookup utility for authoritative and recursive inspection of mail-related records.

Reading time:: 5 min
Difficulty:: Intermediate
Estimated duration:: 5 min
Prerequisites:: None
Last updated:: 2026-07-15
Author:: empire

Overview

CLI DNS lookup utility for authoritative and recursive inspection of mail-related records.

Vendor: ISC / system utility

Primary purpose

Query DNS directly so you can verify SPF, DKIM, DMARC, MX, and PTR publications.

Best for

Operators confirming what authoritative DNS actually serves
Debugging propagation and record syntax issues

Common use cases

Confirm SPF TXT at the organizational domain
Check DKIM selector TXT before enabling signing
Compare authoritative vs recursive answers after a change

Advantages

Precise, scriptable, and available on most operator workstations
No third-party trust boundary for the query itself

Limitations

Does not interpret DMARC policy for you
Easy to query the wrong resolver and misread cache

When not to use it

You need a guided UI explanation of authentication results
You are uncomfortable with a terminal

Pricing

Free with your OS or BIND tools package.

Official website

bind9.readthedocs.io/

Inputs and outputs

Typical inputs

Domain name
Record type
Optional @nameserver

Typical outputs

Raw DNS answers
Status codes

Privacy notes

Review each vendor’s data handling before uploading production lists or message content.

Related learning

DNSDomain Name System — the lookup fabric email authentication depends on.
SPFSender Policy Framework — authorizes hosts that may send for a domain.

Related problems

CNAME at zone apexA CNAME is placed at the zone apex where other record types are also required.
HELO / EHLO problemsThe SMTP HELO/EHLO hostname is missing, invalid, or inconsistent with reverse DNS.
Inconsistent authoritative answersAuthoritative name servers for the same zone return conflicting data.
Incorrect MX targetMX points to the wrong host name or unreachable mail server.
Missing glue recordsDelegation references in-bailiwick name servers without required glue.
MX record missingNo MX record is published for a domain that should receive mail.
NXDOMAIN for expected nameA name that should exist returns NXDOMAIN from authoritative servers.
Reverse DNS mismatchPTR (reverse DNS) for a sending IP is missing or does not match the forward hostname used in mail.
Stale DNS cache after changeResolvers still serve prior answers after an authoritative change because TTL has not expired.
Wrong TTL for cutoverTTL values are too high for a planned cutover, prolonging mixed old/new answers.
Broken SPF includeAn included SPF domain is missing, invalid, or fails closed.
Forwarded email fails SPFForwarding paths break SPF because the forwarder is not authorized.
Incorrect IP authorizationSending infrastructure IPs are not authorized by SPF.
Invalid SPF mechanismSPF record contains unsupported or malformed mechanisms.
Multiple SPF recordsMore than one SPF TXT record exists, causing evaluation failure.
SPF passes but DMARC failsSPF authenticates a domain that does not align for DMARC.
SPF PermErrorSPF evaluation fails permanently due to policy or lookup errors.
SPF record missingNo SPF TXT record is published for the sending domain.
SPF TempErrorTemporary DNS or evaluation failure during SPF checks.
Too many DNS lookupsSPF evaluation exceeds the ten-lookup limit.

Related tools

MXToolboxPopular DNS and mail diagnostics suite for SPF, DMARC, blacklist, and MX checks.
nslookupInteractive DNS lookup utility commonly used for quick MX and TXT checks.
Google Admin Toolbox DigBrowser-based dig-style DNS lookup from Google’s Admin Toolbox.
Google Admin Toolbox CheckMXGoogle Admin Toolbox Check MX for inbound mail DNS sanity checks.
Mail-TesterSend-a-message spam and authentication scoring for pre-send QA.
Kitterman SPF validatorClassic web SPF policy evaluator used by operators for syntax checks.

Workflows

Open step-by-step: Verify DNS recordsVerify zone authority, MX/address records, and authentication-related TXT publications.
Open step-by-step: Configure SPFPublish and validate an SPF policy for authorized senders.
Open step-by-step: Authenticate a new domainPublish SPF, DKIM, and DMARC for a new sending domain and verify authentication before warmup.
Open step-by-step: Migrate authentication recordsMove SPF, DKIM, and DMARC to a new platform without dual-record failures.

Continue Learning

Open step-by-step: Verify DNS recordsVerify zone authority, MX/address records, and authentication-related TXT publications.

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