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SECURITY SCORE
Certificate Information
Subject
CN=mail.nic.cz
Issuer
C=US, O=Let's Encrypt, CN=R13
Valid From
September 24, 2025
Valid Until
December 23, 2025
45 days
Public Key
RSA
4096 bit
Strong
Signature Algorithm
SHA256-RSA
SHA-256 Fingerprint
48:0E:24:BC:F0:19:AA:D9:F7:57:97:6A:17:B3:5E:DF:6E:30:E4:6F:4F:8E:71:BB:E7:29:A1:D9:E9:6E:47:31
Alternative Names
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
Basic
default-src; upgrade-insecure-requests
X-Frame-Options
Good
SAMEORIGIN
X-Content-Type-Options
Good
nosniff
Referrer-Policy
Good
no-referrer
Permissions-Policy
Missing
Not configured
Recommendations
- • Improve CSP by adding more specific directives and removing 'unsafe-inline'
- • Consider adding Permissions-Policy to control browser features
CAA Records (Certificate Authority Authorization)
CAA Records
Not Configured
(Any CA can issue certificates)
CAA Issues
- • No CAA records configured - any CA can issue certificates
Recommendations
- • Implement CAA records to restrict which CAs can issue certificates for your domain
- • This adds an extra layer of security against unauthorized certificate issuance
- • Example: Add CAA record 'example.com. CAA 0 issue "letsencrypt.org"'
- • Consider adding 'iodef' record to receive security incident reports