DNS Gurus
Open Cached · just now
93/100 SECURITY SCORE

Certificate Information

Subject
CN=protonmail.com
Issuer
C=US, O=Let's Encrypt, CN=R13
Valid From
September 29, 2025
Valid Until
December 28, 2025 55 days
Public Key
RSA 4096 bit Strong
Signature Algorithm
SHA256-RSA
SHA-256 Fingerprint
3B:DE:99:CA:B1:0F:B2:71:84:AB:2F:D6:32:5C:37:94:0A:96:39:37:D0:96:74:78:FA:96:45:D2:2B:1D:0F:B8
Alternative Names
10 domains

Security Configuration

TLS Protocols
TLS 1.2 TLS 1.3
Forward Secrecy
Supported (Modern clients use PFS)

HTTP Security Headers

Status
Strict-Transport-Security
Excellent
max-age=31536000; includeSubDomains; preload
Content-Security-Policy
Missing
Not configured
X-Frame-Options
Good
sameorigin
X-Content-Type-Options
Good
nosniff
Referrer-Policy
Good
strict-origin-when-cross-origin
Permissions-Policy
Missing
Not configured
Recommendations
  • • Add Content-Security-Policy header to prevent XSS attacks
  • • Consider adding Permissions-Policy to control browser features

CAA Records (Certificate Authority Authorization)

CAA Records
Configured (Restricts certificate issuance)
Current Issuer
Authorized (Matches CAA policy)
Authorized CAs
swisssign.com comodoca.com digicert.com ; cansignhttpexchanges=yes globalsign.com letsencrypt.org pki.goog ; cansignhttpexchanges=yes sectigo.com ssl.com
Wildcard CAs
comodoca.com digicert.com ; cansignhttpexchanges=yes letsencrypt.org pki.goog ; cansignhttpexchanges=yes ssl.com swisssign.com
Incident Reporting
Recommendations
  • • Consider using critical flag (flags=128) for stricter CAA enforcement
  • • You have authorized 8 CAs - consider limiting to only the CAs you actively use