Identity
49
D
posteo.de
Posture Score: 65/100
Scanned May 10, 2026 at 5:49 AM UTC
Score History
Attack Surface
53
Reputation
92
Identity Findings
TLSA records without DNSSEC for mx01.posteo.de
DANE requires DNSSEC. Without it, TLSA records provide no security benefit and can be spoofed.
💡 Enable DNSSEC for the domain before relying on DANE/TLSA.
Overly broad CIDR range: 2a05:bc0:1000::/47
The /47 CIDR block authorizes a very large IP range to send email as this domain.
💡 Narrow the IP range to only the specific servers that send email.
No DKIM records found
No DKIM records were found for any common selector. Email may not be authenticated.
💡 Configure DKIM signing and publish the public key at <selector>._domainkey.posteo.de
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.
DMARC policy is monitoring-only (p=none)
The p=none policy only monitors; it does not instruct receivers to quarantine or reject unauthenticated mail.
💡 Upgrade to p=quarantine or p=reject after reviewing aggregate reports.
No DMARC aggregate report URI (rua=)
Without rua=, you will not receive aggregate reports about authentication results.
💡 Add rua=mailto:dmarc-reports@posteo.de to your DMARC record.
Very low TTL on MX records: 246s
4 MX records have a TTL of 246s or less (below 300s).
💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.
Very low TTL on NS records: 247s
9 NS records have a TTL of 247s or less (below 300s).
💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.
Very low TTL on TXT records: 246s
2 TXT records have a TTL of 246s or less (below 300s).
💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.
Very low TTL on SPF record: 246s
The SPF record has a TTL of 246s or less (below 300s).
💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.
SPF record length OK (53 bytes)
SPF record is within safe DNS packet size limits.
DKIM cryptographic configuration is compliant
No RFC 8301 compliance issues detected in DKIM key configuration.
No external DMARC report destinations
All DMARC report URIs point to the same domain — no external authorization needed.
Subdomains protected (sp=quarantine)
DMARC subdomain policy enforces quarantine or reject on unauthenticated subdomain mail.
No deprecated DMARCbis tags present
The DMARC record does not use any tags deprecated in DMARCbis (pct, rf, ri).
MX records are valid
All MX records are properly configured.
4 MX records with 4 unique IPs
Multiple MX records provide mail delivery redundancy.
MTA-STS and TLS-RPT are properly configured
MTA-STS policy is enforced and TLS reporting is configured.
TLS-RPT report destinations are reachable
All TLS-RPT rua= URIs point to resolvable domains.
ARC support likely available
MX server software appears to support ARC headers for authentication preservation.
Meets bulk sender authentication requirements
Domain has SPF, DKIM, and DMARC — meeting Google/Yahoo 2024 bulk sender requirements for email authentication.
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.
STARTTLS downgrade resistance is adequate
STARTTLS is supported with modern TLS and protected by MTA-STS and/or DANE.
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=s, aspf=s
DKIM alignment is strict, SPF alignment is strict.
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.
REQUIRETLS not advertised
The primary MX does not advertise REQUIRETLS (RFC 8689). This is an emerging standard — MTA-STS and DANE provide adequate TLS enforcement for most deployments.
DANE/TLSA configured for mx01.posteo.de
TLSA records found and TLS certificate is available for verification.
DANE/TLSA configured for mx02.posteo.de
TLSA records found and TLS certificate is available for verification.
DANE/TLSA configured for mx03.posteo.de
TLSA records found and TLS certificate is available for verification.
DANE/TLSA configured for mx04.posteo.de
TLSA records found and TLS certificate is available for verification.
No BIMI record found
BIMI is not configured. Your brand logo will not display in supporting email clients.
Open mail ports on mx01.posteo.de
Detected open mail-related ports: 25
RFC 8058 one-click unsubscribe assessment
No DKIM signing detected. RFC 8058 one-click unsubscribe requires DKIM-signed List-Unsubscribe headers.
MX IP network diversity
All MX IPs are in the same /16 network. Consider diversifying across networks for resilience.
SOA record parameters
Serial: 1778374852, Refresh: 3600s, Retry: 900s, Expire: 604800s, Min TTL: 300s
Authorized certificate authorities
CAA records restrict certificate issuance to: certum.pl, d-trust.net, geotrust.com
TLSA record TTL: 900s
The TLSA record has a TTL of 900s. Ensure this is shorter than half the certificate validity period.
TLSA record TTL: 900s
The TLSA record has a TTL of 900s. Ensure this is shorter than half the certificate validity period.
TLSA record TTL: 900s
The TLSA record has a TTL of 900s. Ensure this is shorter than half the certificate validity period.
TLSA record TTL: 900s
The TLSA record has a TTL of 900s. Ensure this is shorter than half the certificate validity period.
TLSA record TTL: 900s
The TLSA record has a TTL of 900s. Ensure this is shorter than half the certificate validity period.
Attack Surface Findings
Weak DNSSEC RSA key: 336 bits
The DNSKEY uses an RSA key of 336 bits, below the recommended 2048 bits.
💡 Generate a new DNSKEY with at least 2048-bit RSA or migrate to ECDSA/Ed25519.
Weak DNSSEC RSA key: 336 bits
The DNSKEY uses an RSA key of 336 bits, below the recommended 2048 bits.
💡 Generate a new DNSKEY with at least 2048-bit RSA or migrate to ECDSA/Ed25519.
Non-responsive IP for www.posteo.de: 2a05:bc0:1000::169:1
The subdomain www.posteo.de resolves to 2a05:bc0:1000::169:1 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 2a05:bc0:1000::169:1 is operational or remove the DNS record for www.posteo.de.
Non-responsive IP for www.posteo.de: 2a05:bc0:1000::168:1
The subdomain www.posteo.de resolves to 2a05:bc0:1000::168:1 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 2a05:bc0:1000::168:1 is operational or remove the DNS record for www.posteo.de.
Non-responsive IP for api.posteo.de: 2a05:bc0:1000::168:1
The subdomain api.posteo.de resolves to 2a05:bc0:1000::168:1 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 2a05:bc0:1000::168:1 is operational or remove the DNS record for api.posteo.de.
Non-responsive IP for api.posteo.de: 2a05:bc0:1000::169:1
The subdomain api.posteo.de resolves to 2a05:bc0:1000::169:1 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 2a05:bc0:1000::169:1 is operational or remove the DNS record for api.posteo.de.
Non-responsive IP for cdn.posteo.de: 2a05:bc0:1000::168:1
The subdomain cdn.posteo.de resolves to 2a05:bc0:1000::168:1 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 2a05:bc0:1000::168:1 is operational or remove the DNS record for cdn.posteo.de.
Non-responsive IP for cdn.posteo.de: 2a05:bc0:1000::169:1
The subdomain cdn.posteo.de resolves to 2a05:bc0:1000::169:1 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 2a05:bc0:1000::169:1 is operational or remove the DNS record for cdn.posteo.de.
Non-responsive IP for status.posteo.de: 89.146.220.125
The subdomain status.posteo.de resolves to 89.146.220.125 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 89.146.220.125 is operational or remove the DNS record for status.posteo.de.
DNS ANY query returns 2 record(s)
The DNS server responds to ANY queries with 2 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.
Domain enumerability: low
The domain has low enumerability. Proper NSEC3 configuration and limited CT exposure reduce the attack surface.
Mozilla Autoconfig endpoint detected
The Autoconfig endpoint at autoconfig.posteo.de is publicly accessible and exposes mail server configuration details.
💡 Review the autoconfig XML to ensure it does not expose internal server names or sensitive configuration.
All MX records resolve correctly
No dangling MX records detected — all MX hostnames resolve to valid IP addresses.
Explicit MX records present
The domain has explicit MX records — no implicit A-record fallback delivery.
No internal information leakage detected
No non-routable IP addresses or internal references were found in public DNS records.
9 subdomain(s) discovered for posteo.de
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 posteo.de and its subdomains. Each certificate reveals subdomain names.
NSEC3 authenticated denial of existence
The domain uses NSEC3 with 20 iteration(s) and salt '08857F63AD92DB41'.
3 email SRV record(s) found
Email service SRV records expose mail server configuration for automatic client setup.
DNSSEC is enabled
DNSKEY and/or DS records are present, indicating DNSSEC is configured.
Reputation Findings
Missing domain locks: clientTransferProhibited, clientDeleteProhibited
Domain posteo.de is missing protective locks: clientTransferProhibited, clientDeleteProhibited.
💡 Enable clientTransferProhibited and clientDeleteProhibited locks through your registrar to prevent unauthorized transfers or deletions.
HSTS enabled with preload on posteo.de
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
security.txt present
Found security.txt at https://posteo.de/.well-known/security.txt.
TLS certificate valid for 290 days
Certificate for posteo.de expires on 2027-02-24.
Certificate issued by GeoTrust EV RSA CA G2
The certificate for posteo.de is issued by a third-party CA.
Signature algorithm: rsa-sha384
The certificate for posteo.de uses an acceptable signature algorithm.
RSA key: 3072 bits
The certificate for posteo.de uses an adequate RSA key of 3072 bits.
SCTs present in certificate
The certificate for posteo.de contains Signed Certificate Timestamps.
No weak ciphers detected
No known weak cipher suites detected on posteo.de.
TLD has good reputation
The .de TLD is not on known abuse watchlists.
DMARC reporting destinations look legitimate
DMARC rua/ruf addresses do not point to known URL shortener services.
MX records point to stable infrastructure
No MX records point to known dynamic DNS service domains.
Strong TLS configuration on primary MX
Primary MX (mx04.posteo.de) uses TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 including Forward Secrecy.
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.posteo.de
HTTPS request to https://webmail.posteo.de failed or timed out.
WHOIS registration data
Registrar: Unknown | Created: Unknown | Expires: Unknown | Updated: Unknown
WHOIS privacy protection not detected
Domain posteo.de does not appear to have WHOIS privacy protection. Registrant details may be publicly visible.
Typosquat detected: osteo.de (has MX!), psteo.de (has MX!), poteo.de (has MX!), poseo.de (has MX!), posto.de (has MX!)
27 registered lookalike domain(s) that could be used for phishing against your brand. Showing top 5 of 27. Domains with MX records can send and receive email, making them high-risk phishing vectors.
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: none
DMARC Authentication Chain (DKIM)
DMARC uses DKIM to verify that emails have not been tampered with
DKIM Signature
DKIM signature missing
→
DMARC Policy
DMARC policy: none
⚠️ DKIM signature is missing. DMARC relies on DKIM to verify email integrity and prevent tampering. Without DKIM, DMARC alignment will fail for cryptographic verification.
Mail Server Identity: mx01.posteo.de
PTR record proves mail server legitimacy
MX: mx01.posteo.de
Mail server at 185.67.36.62
→
PTR Record
Reverse DNS: mx01.posteo.de
Mail Server Identity: mx02.posteo.de
PTR record proves mail server legitimacy
MX: mx02.posteo.de
Mail server at 185.67.36.73
→
PTR Record
Reverse DNS: mx02.posteo.de
Mail Server Identity: mx03.posteo.de
PTR record proves mail server legitimacy
MX: mx03.posteo.de
Mail server at 185.67.36.63
→
PTR Record
Reverse DNS: mx03.posteo.de
Mail Server Identity: mx04.posteo.de
PTR record proves mail server legitimacy
MX: mx04.posteo.de
Mail server at 185.67.36.71
→
PTR Record
Reverse DNS: mx04.posteo.de
Mail Server Reputation: mx01.posteo.de
RBL check ensures server is not blacklisted
MX: mx01.posteo.de
Mail server at 185.67.36.62
→
RBL Status
Not blacklisted
Mail Server Reputation: mx02.posteo.de
RBL check ensures server is not blacklisted
MX: mx02.posteo.de
Mail server at 185.67.36.73
→
RBL Status
Not blacklisted
Mail Server Reputation: mx03.posteo.de
RBL check ensures server is not blacklisted
MX: mx03.posteo.de
Mail server at 185.67.36.63
→
RBL Status
Not blacklisted
Mail Server Reputation: mx04.posteo.de
RBL check ensures server is not blacklisted
MX: mx04.posteo.de
Mail server at 185.67.36.71
→
RBL Status
Not blacklisted
Enforced Encryption Chain
MTA-STS enforces TLS encryption to prevent man-in-the-middle attacks
TLS Support
Mail servers support TLS encryption
→
MTA-STS Policy
Mode: enforce
Brand Identity Chain
BIMI displays your logo in email clients, but requires DMARC enforcement
DMARC Enforcement
DMARC not enforced (p=none or missing)
→
BIMI Record
BIMI not configured
⚠️ DMARC is not enforced. BIMI requires a DMARC policy of "quarantine" or "reject" to prove you have strong email authentication. Without enforcement, email clients will not display your logo.
TLS Monitoring Chain
TLS-RPT provides reports about TLS connection failures
TLS Support
Mail servers support TLS encryption
→
TLS-RPT Reporting
TLS failure reporting configured
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/posteo.de.svg" alt="Email Security Grade">
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