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nslookup

nslookup

Interactive DNS lookup utility commonly used for quick MX and TXT checks.

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

Overview

Interactive DNS lookup utility commonly used for quick MX and TXT checks.

Vendor: System utility

Primary purpose

Perform quick DNS lookups when dig is unavailable.

Best for

Fast MX/TXT checks on Windows and mixed environments

Common use cases

Confirm MX targets
Spot-check SPF TXT

Advantages

Widely available
Simple interactive mode

Limitations

Less precise control than dig
Resolver behavior varies by OS

When not to use it

You need detailed DNSSEC or authoritative debugging (prefer dig)

Pricing

Free with the OS.

Official website

Inputs and outputs

Typical inputs

Domain name
Record type

Typical outputs

Resolver answers

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.

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.

Related tools

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

Workflows

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

Continue Learning

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

Previousdig NextGoogle Admin Toolbox Dig

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