The toolbox that
actually explains things
Free email header analysis, DNS lookups, SPF / DKIM / DMARC validation and building, WHOIS, subnet calculation and more.
Analyze email headersEmail Header Analyzer
Decode SPF, DKIM, DMARC, and routing hops from raw email headers. Pinpoint delivery issues instantly.
DNS Lookup
Query A, AAAA, MX, TXT, NS, CNAME, and CAA records via Cloudflare DNS.
MX Record Checker
Validate MX records, check priority ordering, confirm each mail server resolves.
SPF Record Checker
Validate SPF records, check DNS lookup limits, decode mechanisms, and find issues.
DMARC Record Checker
Validate DMARC records, decode every tag, check policy strength, verify report destinations.
DKIM Record Checker
Look up DKIM public keys by domain and selector. Validates key strength, auto-discovers selectors.
SPF Record Builder
Build SPF records interactively. Add providers with one click, track DNS lookup count live.
DMARC Record Builder
Build a DMARC record step by step with plain-English guidance for every option.
WHOIS Lookup
Domain registration data via RDAP — registration dates, expiry, registrar, and nameservers.
PTR / Reverse DNS
Look up PTR records for IPv4/IPv6 addresses and verify forward-confirmed rDNS.
Subnet Calculator
IPv4 and IPv6 CIDR breakdown: network address, host ranges, masks, and binary.
Blacklist Checker
Check an IP or domain against 100+ DNSBLs simultaneously.
IP Geolocation
Country, ASN, ISP, and network info for any IP address.
SSL/TLS Checker
Certificate expiry, chain validity, and cipher support for any domain.