Free DNS And Email Security Tools
Run DNS lookups, check SPF, DMARC and DKIM, compare DNS propagation, audit domain configuration, discover subdomains, and work with IP addresses and subnets without bouncing between separate tools. Start with a guided path or open the exact checker, lookup, or guide you need.
Start With The Right Tool
Check Email Security
Review SPF, DMARC, DKIM, MTA-STS, TLS-RPT, and BIMI together when you need a fast mail posture check.
Audit A Domain
Start here if you are troubleshooting a setup, preparing a migration, or checking for obvious DNS and mail issues.
Look Up A Specific Record
Use a focused lookup when you already know the record type you need to inspect, compare, or export.
Learn Before You Change Anything
Use the guides if you need a clearer mental model before editing live DNS or email authentication records.
Popular Starting Points
Browse All Tools
Discovery
Subdomain Finder
Search certificate transparency data for related hostnames.
Hosted Service Fingerprint Finder
Identify likely hosted platforms and services from DNS clues.
CNAME Discovery
Discover CNAME records in use and identify likely linked services.
Certificate SAN Explorer
Fetch a TLS certificate and list its SAN hostnames.
DKIM Selector Finder
Try common selectors and discover likely DKIM records.
Record Lookups
Record Lookup
Query A, AAAA, CNAME, NS, PTR, SOA, SRV, CAA, and TXT records.
NS Lookup
Check authoritative nameserver records directly.
MX Lookup
Check mail exchange records, priorities, and resolved IPs.
TXT Lookup
Check TXT records, TTL values, and full text content.
CAA Analysis
Review certificate authority authorization records and tags.
PTR Check
Validate reverse DNS and forward-confirmed PTR results.
SRV Lookup
Query SRV records with service and protocol inputs.
Email & Security
SPF Checker
Break down SPF mechanisms, redirects, includes, and lookup count.
SPF Generator
Build an SPF record from common mechanisms and review estimated lookup cost.
SPF Flattener
Generate a flattened SPF-style output from the current effective SPF policy.
DMARC Checker
Inspect DMARC policy, reporting, and alignment tags.
DKIM Checker
Check DKIM records with a selector.
Email Security Check
Review SPF, DMARC, DKIM, MTA-STS, TLS-RPT, and BIMI together.
MTA-STS Check
Check the MTA-STS TXT record and HTTPS policy file.
TLS-RPT Check
Inspect TLS-RPT reporting records.
BIMI Check
Inspect BIMI TXT records and parsed BIMI tags.
Blacklist Checker
Check whether a domain or IP appears on common blocklists.
Email Header Analysis
Analyze email headers for SPF, DKIM, DMARC, and routing clues.
Email Provider Setup Checker
Compare Google Workspace or Microsoft 365 mail DNS patterns.
Domain Intelligence
DNS Audit
Run a broad DNS and email configuration audit.
Domain DNS Summary
See a broad one-page view of key DNS records for a domain.
Delegation Checker
Compare parent delegation, child NS records, and SOA serials.
Whois Lookup
Inspect domain registration, registrar, and nameserver information.
DNSSEC Checker
Check whether DNSKEY and DS records are present.
DNS Propagation Checker
Compare answers across public resolvers.
Glue Record Checker
Inspect in-bailiwick nameservers and glue-related addressing.
Dangling CNAME Checker
Check whether a CNAME target looks dead or takeover-prone.
Networking Tools
Subnet Calculator
Calculate network range, usable hosts, subnet mask, broadcast address, and more.
Private vs Public IP Checker
Check whether an IPv4 address is private, public, or special-use.
CIDR ↔ Subnet Mask Converter
Convert between CIDR notation and dotted-decimal subnet masks.
Reverse PTR Zone Helper
Generate reverse PTR record format and suggested reverse DNS zone names.
Learning Articles
What Is APIPA? 169.254.x.x Explained
Learn what APIPA means, why devices assign 169.254.x.x addresses, what it says about DHCP problems, and how to troubleshoot a link-local IP quickly.
What Is DNS TTL? Time to Live Explained
Learn what DNS TTL means, how DNS caching works, why TTL affects propagation and reliability, and how to choose the right TTL before a DNS change.
Check Certificate SANs And Hostname Coverage
Learn how to check certificate SANs, confirm whether a hostname is covered, and use SAN data to troubleshoot TLS errors and asset exposure.
How to Fix SPF Softfail
A practical guide to fixing SPF softfail, including how to identify the sending domain, review the SPF policy, authorise senders, and tighten enforcement safely.
Fix CAA Record Errors Before Certificate Renewal
Learn how to fix CAA record errors, why certificate issuance gets blocked, and how to verify issue, issuewild, and parent-domain policy before renewal fails.
Google Workspace SPF, DKIM, and DMARC Setup
A practical guide to setting up SPF, DKIM, and DMARC for Google Workspace, including what to publish in DNS and what to verify after setup.
How to Check a DKIM Record
A practical guide to checking a DKIM record, finding the right selector, validating the TXT record, and spotting common DKIM setup problems.
How to Check a DMARC Record
A practical guide to checking a DMARC record, understanding the main tags, and spotting common DMARC issues before enforcement causes problems.
What DNS Pro is for
DNS Pro is designed to make DNS audits, email authentication checks, domain troubleshooting, and related network calculations easier to work through. The goal is to turn raw infrastructure data into practical answers you can act on when you are fixing delivery issues, validating a migration, or checking whether a domain is configured safely.
DNS Lookup, Domain Security And Network Utilities
Use the record lookup tools for A, AAAA, CNAME, MX, NS, TXT, PTR, SRV and CAA queries. For broader troubleshooting, run a DNS audit, compare public resolver propagation, inspect DNSSEC and delegation, or review WHOIS and RDAP registration data.
Email administrators can validate SPF lookup limits, DKIM selectors, DMARC alignment and policy, BIMI, MTA-STS and TLS reporting. Network utilities cover subnet calculation, CIDR conversion, public and private IP classification, and reverse DNS preparation.