SSL/TLS check
Checks your certificate’s validity and chain, the TLS versions you have enabled and the cipher suites you accept, and lists outdated or weak settings with steps to fix them.
Other tests
Security headers test
Grades HSTS, CSP and cookie settings.
Email security check
SPF, DKIM and DMARC: can someone send fake email in your name?
External surface discovery
Your subdomains that show up in public records.