Network, DNS & email diagnostics
Check MX, SPF, DKIM, DMARC, blacklists, SSL, DNS and more for any domain, IP, email or URL.
Type a domain, IP, email or URL and pick a check, or a prefix like Pick a check, or type a prefix like spf: · press / to search
- Diagnose an Errornew
Paste a bounce, NDR, or SMTP error — get an instant diagnosis of the failure and the exact fix, then auto-run the relevant checks.
- Domain Health
Full battery: DNS, mail, SPF/DKIM/DMARC, blacklists, SMTP — graded.
- Live Mail Test
Send us an email, we score SPF, DKIM, DMARC, reverse DNS and the delivery chain.
- Email Header Analyzer
Parse Received chains, per-hop delays and authentication results.
- MX Lookup
Mail exchanger records with resolved IPs and sanity checks.
- SPF Check
Fetch and parse SPF, resolve includes, count DNS lookups (max 10).
- DKIM Check
Fetch a DKIM key by selector, or probe common selectors.
- DMARC Check
Fetch and parse the _dmarc policy record.
- Blacklist Check
Check an IP or host against ~40 live DNS blocklists in parallel.
- HTTPS / TLS Check
Full TLS certificate inspection: chain, SANs, expiry, protocol.
- A Record
IPv4 address records for a hostname.
- DNS Propagation
Compare answers from public resolvers around the world.
- Whois Lookup
Registrar, dates, nameservers and status for a domain or IP.
- Ping
ICMP echo round-trip times and packet loss.
- Traceroute
Network path to a host with per-hop latency.
- AAAA Record
IPv6 address records for a hostname.
- ASN Lookup
Origin AS, prefix, and AS name for an IP (Team Cymru).
- BIMI Check
Brand-indicator record: logo URL and verified-mark certificate.
- Bulk Lookup
Run a lookup across up to 100 targets; export CSV.
- CAA Lookup
Certification Authority Authorization records.
- CERT Record
Certificate records stored in DNS (RFC 4398).
- CNAME Lookup
Canonical-name (alias) record for a hostname.
- DMARC Delivery Reporton-demand
On-demand DMARC posture snapshot (no report ingestion).
- DMARC Generator
Build a DMARC policy record with a plain-English explanation.
- DMARC Report Analyzer
Parse DMARC aggregate (RUA) reports — XML, .gz or .zip.
- DNS Server Audit
Audit a domain’s nameservers: consistency, recursion, delegation health.
- DNSKEY Lookup
DNSSEC public keys with key tags, roles and algorithms.
- DS Lookup
Delegation Signer records in the parent zone.
- Email Deliverabilityone-shot
One-shot deliverability score: SPF, DKIM, DMARC, rDNS, TLS, blacklists.
- Google/Yahoo Compliance
Grade a domain against Google & Yahoo bulk-sender requirements.
- HTTP Check
Follow redirects; status chain, headers and response time.
- IPSECKEY Record
IPsec keying material published in DNS.
- LOC Record
Geographic location records (RFC 1876).
- MailFlow Monitoron-demand
On-demand mail-flow health snapshot (no continuous monitoring).
- Microsoft Compliance
Grade a domain against Microsoft sender requirements.
- MTA-STS Check
MTA-STS DNS record plus the published policy file.
- NSEC Lookup
Authenticated denial-of-existence records.
- NSEC3PARAM
NSEC3 hashing parameters for the zone.
- RDAP / ARIN Lookup
IP address block registration data via RDAP.
- Reverse DNS (PTR)
PTR record for an IP address (reverse DNS).
- RRSIG Lookup
DNSSEC signatures with validity windows.
- SMTP Diagnostics
Banner, capabilities, STARTTLS, open-relay and reverse-DNS checks.
- SOA Record
Start-of-authority: serial, refresh, retry, expire, minimum.
- SPF FlatteningPro
Keep SPF under 10 lookups: ProbeKit hosts a flattened record and refreshes it when your providers change.
- SPF Generator
Build a valid SPF record from your senders.
- SRV Lookup
Service records (_service._proto.name) with priority, weight, port, target.
- TCP Port Test
Test whether a TCP port is open, closed or filtered.
- TLS-RPT Check
SMTP TLS reporting record (_smtp._tls).
- TXT Lookup
All text records published on a domain.
- What Is My IP
Your public IP address and approximate location.
- AI Crawler Access
Analyze robots.txt rules for GPTBot, ClaudeBot, CCBot and friends.
- Email Extraction
Extract and dedupe email addresses from pasted text; export CSV.
- llms.txt Check
Fetch /llms.txt and /llms-full.txt and report their contents.
- Password Generator
Strong random passwords, generated locally in your browser.
- Subnet Calculator
CIDR math: network, broadcast, mask, usable range, host count.
- Typosquat Scanheavy
Generate ~180 lookalike domains and find which ones are registered and resolving.