16 tools · no signup · runs in seconds
Fix email deliverability
before it breaks trust.
Validate SPF, DKIM, and DMARC, trace DNS propagation, and catch security exposures — the diagnostics MXToolbox charges for, free.
Email Authentication
DNS Records
Diagnostics
DIAG-01
DNS Propagation
Compare answers across 4 public resolvers
DIAG-02
Subdomain Scanner
Discover common subdomains
DIAG-03
WHOIS Lookup
Registrar and registration data
MAIL-04
SMTP Banner
Read a mail server's greeting
MAIL-05
STARTTLS Checker
Confirm mail encryption support
DIAG-04
Domain Age
Registration date and age
Security
SEC-01
Blacklist Checker
Check against major RBLs
SEC-02
AXFR Checker
Test for exposed zone transfers
SEC-03
SMTP Port Tester
Probe mail and web ports
SEC-04
Domain Reputation
Composite deliverability + safety score
SEC-05
DNSSEC Checker
Verify DNS is cryptographically signed
SEC-06
Open Relay Test
Detect abusable mail relays