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.
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- 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.