Identity
9
D
kernel.org
Posture Score: 64/100
Scanned May 8, 2026 at 8:15 AM UTC
Attack Surface
91
Reputation
91
Identity Findings
Weak DKIM RSA key (~1296 bits) for selector 'default'
RSA keys shorter than 2048 bits are considered weak. Current key is approximately 1296 bits.
💡 Generate a new 2048-bit (or larger) RSA key pair and update the DKIM record.
No STARTTLS support on smtp1.kernel.org:25
The mail server does not advertise STARTTLS, meaning email is transmitted in plaintext.
💡 Enable STARTTLS on the mail server.
No STARTTLS support on smtp2.kernel.org:25
The mail server does not advertise STARTTLS, meaning email is transmitted in plaintext.
💡 Enable STARTTLS on the mail server.
No STARTTLS support on smtp3.kernel.org:25
The mail server does not advertise STARTTLS, meaning email is transmitted in plaintext.
💡 Enable STARTTLS on the mail server.
No STARTTLS support on smtp1.kernel.org
The mail server does not support STARTTLS. All email is transmitted in plaintext.
💡 Enable STARTTLS on the mail server.
No STARTTLS support on smtp2.kernel.org
The mail server does not support STARTTLS. All email is transmitted in plaintext.
💡 Enable STARTTLS on the mail server.
No STARTTLS support on smtp3.kernel.org
The mail server does not support STARTTLS. All email is transmitted in plaintext.
💡 Enable STARTTLS on the mail server.
NS delegation mismatch
The registrar-delegated nameservers do not match the zone NS records.
💡 Update either the registrar NS delegation or the zone NS records to match.
No MTA-STS record found
Without MTA-STS, mail transport encryption cannot be enforced and is vulnerable to downgrade attacks.
💡 Publish a _mta-sts TXT record and host a policy file at https://mta-sts.kernel.org/.well-known/mta-sts.txt
STARTTLS without MTA-STS or DANE protection
STARTTLS alone is vulnerable to downgrade attacks. Neither MTA-STS nor DANE is configured to enforce encryption.
💡 Deploy MTA-STS and/or DANE to protect against STARTTLS stripping attacks.
Generic ISP PTR hostname: ec2-35-83-38-47.us-west-2.compute.amazonaws.com
The PTR record for 35.83.38.47 appears to be a generic ISP hostname, which can harm deliverability.
💡 Set a meaningful PTR record like mail.kernel.org
Generic ISP PTR hostname: ec2-35-85-114-177.us-west-2.compute.amazonaws.com
The PTR record for 35.85.114.177 appears to be a generic ISP hostname, which can harm deliverability.
💡 Set a meaningful PTR record like mail.kernel.org
Generic ISP PTR hostname: ec2-44-230-10-245.us-west-2.compute.amazonaws.com
The PTR record for 44.230.10.245 appears to be a generic ISP hostname, which can harm deliverability.
💡 Set a meaningful PTR record like mail.kernel.org
No CAA records found
No CAA records are configured. Any certificate authority can issue certificates for this domain.
💡 Add CAA records to restrict certificate issuance. Example: 0 issue "letsencrypt.org"
No TLS-RPT record found
Without TLS-RPT, you will not receive reports about TLS negotiation failures.
💡 Publish a _smtp._tls TXT record (e.g. "v=TLSRPTv1; rua=mailto:tls-reports@kernel.org").
Very low TTL on MX records: 251s
3 MX records have a TTL of 251s or less (below 300s).
💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.
NS TTL mismatch between parent and authoritative zone
The NS record TTL in the parent zone (~7151s) differs significantly from the authoritative zone (~86400s).
💡 Align NS record TTLs between the parent zone delegation and the authoritative zone.
SPF record is valid
The SPF record is properly configured with valid syntax and within lookup limits.
DKIM cryptographic configuration is compliant
No RFC 8301 compliance issues detected in DKIM key configuration.
No deprecated DMARCbis tags present
The DMARC record does not use any tags deprecated in DMARCbis (pct, rf, ri).
ARC support likely available
MX server software appears to support ARC headers for authentication preservation.
SMTP security checks passed
No open relay, VRFY/EXPN, or banner disclosure issues detected.
SMTP RFC 5321 compliance checks passed
The mail server accepts postmaster@ and abuse@ and uses a valid FQDN in EHLO.
IPv6 readiness is good
IPv6 records are present and properly configured.
DNS responses are consistent across all nameservers
All authoritative nameservers return consistent answers with proper AA flags.
DKIM2 not detected
No DKIM key record with v=2 was found across common selectors. DKIM2 is an emerging standard and not yet widely deployed.
DMARC alignment: adkim=r, aspf=r
DKIM alignment is relaxed, SPF alignment is relaxed.
DMARCbis np tag absent
The DMARC record does not include the np (non-existent subdomain policy) tag. Consider adding np=reject to protect non-existent subdomains under DMARCbis.
DMARCbis psd tag absent
The DMARC record does not include the psd (public suffix domain) indicator. Consider adding psd=n to explicitly identify this as an organizational domain.
No DANE/TLSA records found
DANE is not configured for any MX server. This is optional but provides strong certificate binding.
No BIMI record found
BIMI is not configured. Your brand logo will not display in supporting email clients.
Open mail ports on smtp1.kernel.org
Detected open mail-related ports: 25, 465, 587
RFC 8058 one-click unsubscribe assessment
DKIM signing is configured. RFC 8058 compliance depends on List-Unsubscribe and List-Unsubscribe-Post headers being included in outbound messages and DKIM signatures.
MX IP network diversity
MX IPs span 3 different /16 networks, providing good diversity.
SOA record parameters
Serial: 2015014567, Refresh: 43200s, Retry: 3600s, Expire: 1209600s, Min TTL: 180s
Attack Surface Findings
Domain enumerability: medium
The domain has moderate enumerability. CT logs and DNS records reveal significant information about the domain structure.
💡 Restrict zone transfers, use NSEC3 instead of NSEC, consider wildcard certificates to reduce CT log exposure, and implement rate limiting on DNS queries.
DNSSEC is not enabled
No DNSKEY or DS records were found. DNS responses are not cryptographically authenticated.
💡 Enable DNSSEC by generating DNSKEY records and publishing DS records at the registrar.
DNS ANY query returns 17 record(s)
The DNS server responds to ANY queries with 17 record(s). The low record count limits amplification risk, but ANY responses still aid reconnaissance.
💡 Configure the DNS server to refuse or minimize ANY query responses per RFC 8482.
No internal information leakage detected
No non-routable IP addresses or internal references were found in public DNS records.
No email autodiscovery endpoints detected
No Microsoft Autodiscover, Mozilla Autoconfig, or email SRV records were found.
10 subdomain(s) discovered for kernel.org
Subdomains were enumerated via Certificate Transparency logs, DNS wordlist brute-forcing, and DNS record analysis.
0 certificate(s) found in CT logs
Certificate Transparency logs contain 0 certificate(s) for kernel.org and its subdomains. Each certificate reveals subdomain names.
Reputation Findings
Missing domain locks: clientDeleteProhibited
Domain kernel.org is missing protective locks: clientDeleteProhibited.
💡 Enable clientTransferProhibited and clientDeleteProhibited locks through your registrar to prevent unauthorized transfers or deletions.
HSTS enabled but missing preload directive on kernel.org
Strict-Transport-Security: max-age=15768001
💡 Add the "preload" directive to the HSTS header and submit the domain to hstspreload.org.
security.txt present
Found security.txt at https://kernel.org/.well-known/security.txt.
TLS certificate valid for 68 days
Certificate for kernel.org expires on 2026-07-15.
Certificate issued by E8
The certificate for kernel.org is issued by a third-party CA.
Signature algorithm: ecdsa-with-sha384
The certificate for kernel.org uses an acceptable signature algorithm.
ECC key: 256 bits
The certificate for kernel.org uses an adequate ECC key of 256 bits.
SCTs present in certificate
The certificate for kernel.org contains Signed Certificate Timestamps.
No weak ciphers detected
No known weak cipher suites detected on kernel.org.
Domain valid for 303 days
Domain kernel.org expires on 2027-03-08.
Google Safe Browsing DNS check — no flag detected
DNS-based Safe Browsing lookup returned no results. Full verification requires the Google Safe Browsing API key.
Abuse contact lookup failed
Could not query abuse contact information.
PhishTank — API key required
PhishTank phishing database check requires an API key.
Sender Score — API key required
Sender Score reputation check requires an API key.
Cisco Talos — API key required
Cisco Talos IP reputation check requires an API key.
Could not connect to webmail.kernel.org
HTTPS request to https://webmail.kernel.org failed or timed out.
WHOIS registration data
Registrar: Gandi SAS | Created: 1997-03-07 | Expires: 2027-03-08 | Updated: 2025-05-28
WHOIS privacy protection enabled
Domain kernel.org has WHOIS privacy/redaction enabled.
Dependency Chains
DMARC Authentication Chain (SPF)
DMARC uses SPF to verify that emails come from authorized servers
SPF Record
SPF record found and configured
→
DMARC Policy
DMARC policy: quarantine
DMARC Authentication Chain (DKIM)
DMARC uses DKIM to verify that emails have not been tampered with
DKIM Signature
DKIM signature configured
→
DMARC Policy
DMARC policy: quarantine
Mail Server Identity: smtp1.kernel.org
PTR record proves mail server legitimacy
MX: smtp1.kernel.org
Mail server at 35.83.38.47
→
PTR Record
Reverse DNS: ec2-35-83-38-47.us-west-2.compute.amazonaws.com
Mail Server Identity: smtp2.kernel.org
PTR record proves mail server legitimacy
MX: smtp2.kernel.org
Mail server at 35.85.114.177
→
PTR Record
Reverse DNS: ec2-35-85-114-177.us-west-2.compute.amazonaws.com
Mail Server Identity: smtp3.kernel.org
PTR record proves mail server legitimacy
MX: smtp3.kernel.org
Mail server at 44.230.10.245
→
PTR Record
Reverse DNS: ec2-44-230-10-245.us-west-2.compute.amazonaws.com
Mail Server Reputation: smtp1.kernel.org
RBL check ensures server is not blacklisted
MX: smtp1.kernel.org
Mail server at 35.83.38.47
→
RBL Status
Not blacklisted
Mail Server Reputation: smtp2.kernel.org
RBL check ensures server is not blacklisted
MX: smtp2.kernel.org
Mail server at 35.85.114.177
→
RBL Status
Not blacklisted
Mail Server Reputation: smtp3.kernel.org
RBL check ensures server is not blacklisted
MX: smtp3.kernel.org
Mail server at 44.230.10.245
→
RBL Status
Not blacklisted
Enforced Encryption Chain
MTA-STS enforces TLS encryption to prevent man-in-the-middle attacks
TLS Support
TLS not verified or unsupported
→
MTA-STS Policy
MTA-STS not configured
⚠️ TLS support could not be verified. MTA-STS requires TLS to enforce encrypted connections. Without TLS, MTA-STS cannot function.
Brand Identity Chain
BIMI displays your logo in email clients, but requires DMARC enforcement
DMARC Enforcement
DMARC policy: quarantine
→
BIMI Record
BIMI not configured
⚠️ BIMI record is missing. Even with DMARC enforcement, you need to configure BIMI to display your brand logo in supported email clients.
TLS Monitoring Chain
TLS-RPT provides reports about TLS connection failures
TLS Support
TLS not verified or unsupported
→
TLS-RPT Reporting
TLS-RPT not configured
⚠️ TLS support could not be verified. TLS-RPT reports on TLS connection failures, but without TLS support, there's nothing to monitor. You need working TLS encryption before TLS-RPT can provide value.
Security Checks
MX Records
✓
SPF Record
✓
DKIM Record
✓
DMARC Policy
✓
BIMI Record
✗
CAA Records
✗
DNSSEC
✗
MTA-STS
✗
TLS-RPT
✗
Embed Badge
Display your domain's security grade on your website or README:
<img src="https://scan.ractermx.com/badge/kernel.org.svg" alt="Email Security Grade">
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