Identity
68
C
offerup.com
Posture Score: 78/100
Scanned May 8, 2026 at 5:35 PM UTC
Attack Surface
76
Reputation
91
Identity Findings
SPF exceeds 10-lookup limit (11 lookups)
RFC 7208 limits SPF to 10 DNS lookups. Exceeding this causes PermError and SPF failures.
💡 Flatten your SPF record by replacing includes with direct ip4/ip6 mechanisms.
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.offerup.com/.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.
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@offerup.com").
ARC support not detected
No evidence of ARC (Authenticated Received Chain) support on MX servers. Forwarded messages may lose authentication.
💡 Consider enabling ARC signing on your mail servers to preserve authentication through forwarding.
Shared IP 170.10.128.221 used by multiple MX servers
The IP 170.10.128.221 is shared across 2 MX hostnames, reducing redundancy.
💡 Use unique IP addresses for each MX server for better redundancy.
Shared IP 170.10.128.141 used by multiple MX servers
The IP 170.10.128.141 is shared across 2 MX hostnames, reducing redundancy.
💡 Use unique IP addresses for each MX server for better redundancy.
Shared IP 170.10.132.242 used by multiple MX servers
The IP 170.10.132.242 is shared across 2 MX hostnames, reducing redundancy.
💡 Use unique IP addresses for each MX server for better redundancy.
Shared IP 170.10.132.141 used by multiple MX servers
The IP 170.10.132.141 is shared across 2 MX hostnames, reducing redundancy.
💡 Use unique IP addresses for each MX server for better redundancy.
Shared IP 170.10.132.221 used by multiple MX servers
The IP 170.10.132.221 is shared across 2 MX hostnames, reducing redundancy.
💡 Use unique IP addresses for each MX server for better redundancy.
Shared IP 170.10.128.242 used by multiple MX servers
The IP 170.10.128.242 is shared across 2 MX hostnames, reducing redundancy.
💡 Use unique IP addresses for each MX server for better redundancy.
Very low TTL on TXT records: 99s
24 TXT records have a TTL of 99s or less (below 300s).
💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.
Very low TTL on SPF record: 99s
The SPF record has a TTL of 99s or less (below 300s).
💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.
Very low TTL on DMARC record: 279s
The DMARC record has a TTL of 279s 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 (~7179s) differs significantly from the authoritative zone (~86400s).
💡 Align NS record TTLs between the parent zone delegation and the authoritative zone.
DKIM records are valid
DKIM records found and validated for selectors: google
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).
MX records are valid
All MX records are properly configured.
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.
NS delegation is properly configured
All nameservers are responsive, consistent, and properly secured.
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 us-smtp-inbound-2.mimecast.com
Detected open mail-related ports: 25, 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
All MX IPs are in the same /16 network. Consider diversifying across networks for resilience.
SOA record parameters
Serial: 2403225406, Refresh: 10000s, Retry: 2400s, Expire: 604800s, Min TTL: 1800s
Attack Surface Findings
NSEC records enable zone walking
The domain uses NSEC records for DNSSEC authenticated denial of existence. NSEC records can be walked to enumerate all names in the zone, effectively disclosing the entire zone contents.
💡 Switch from NSEC to NSEC3 with opt-out to prevent zone enumeration. Use NSEC3 with a random salt and sufficient iterations.
Domain enumerability: high
The domain is highly enumerable. Zone transfers, NSEC zone walking, or a combination of factors make it easy to discover all DNS records.
💡 Restrict zone transfers, use NSEC3 instead of NSEC, consider wildcard certificates to reduce CT log exposure, and implement rate limiting on DNS queries.
Non-responsive IP for support.offerup.com: 184.168.221.14
The subdomain support.offerup.com resolves to 184.168.221.14 which is not responding on ports 80 or 443. This may indicate a decommissioned server.
💡 Verify the server at 184.168.221.14 is operational or remove the DNS record for support.offerup.com.
NSEC used instead of NSEC3 (zone enumeration possible)
The domain uses NSEC records for authenticated denial of existence. NSEC allows zone walking.
💡 Migrate from NSEC to NSEC3 to prevent zone enumeration.
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.
7 subdomain(s) discovered for offerup.com
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 offerup.com and its subdomains. Each certificate reveals subdomain names.
DNSSEC is enabled
DNSKEY and/or DS records are present, indicating DNSSEC is configured.
Reputation Findings
Missing domain locks: clientDeleteProhibited
Domain offerup.com 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 offerup.com
Strict-Transport-Security: max-age=2592000
💡 Add the "preload" directive to the HSTS header and submit the domain to hstspreload.org.
security.txt present
Found security.txt at https://offerup.com/.well-known/security.txt.
TLS certificate valid for 46 days
Certificate for offerup.com expires on 2026-06-23.
Certificate issued by WE1
The certificate for offerup.com is issued by a third-party CA.
Signature algorithm: ecdsa-with-sha256
The certificate for offerup.com uses an acceptable signature algorithm.
ECC key: 256 bits
The certificate for offerup.com uses an adequate ECC key of 256 bits.
SCTs present in certificate
The certificate for offerup.com contains Signed Certificate Timestamps.
No weak ciphers detected
No known weak cipher suites detected on offerup.com.
Domain valid for 139 days
Domain offerup.com expires on 2026-09-25.
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.offerup.com
HTTPS request to https://webmail.offerup.com failed or timed out.
WHOIS registration data
Registrar: GoDaddy Corporate Domains, LLC | Created: 2002-09-24 | Expires: 2026-09-25 | Updated: 2025-08-25
WHOIS privacy protection not detected
Domain offerup.com does not appear to have WHOIS privacy protection. Registrant details may be publicly visible.
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: reject
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: reject
⚠️ 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: us-smtp-inbound-2.mimecast.com
PTR record proves mail server legitimacy
MX: us-smtp-inbound-2.mimecast.com
Mail server at 170.10.128.221
→
PTR Record
Reverse DNS: us-smtp-inbound-2.mimecast.com
Mail Server Identity: us-smtp-inbound-1.mimecast.com
PTR record proves mail server legitimacy
MX: us-smtp-inbound-1.mimecast.com
Mail server at 170.10.128.242
→
PTR Record
Reverse DNS: us-smtp-inbound-1.mimecast.com
Mail Server Reputation: us-smtp-inbound-2.mimecast.com
RBL check ensures server is not blacklisted
MX: us-smtp-inbound-2.mimecast.com
Mail server at 170.10.128.221
→
RBL Status
Not blacklisted
Mail Server Reputation: us-smtp-inbound-1.mimecast.com
RBL check ensures server is not blacklisted
MX: us-smtp-inbound-1.mimecast.com
Mail server at 170.10.128.242
→
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
MTA-STS not configured
⚠️ MTA-STS policy is missing. Even with TLS support, you lack the enforcement layer that prevents attackers from stripping encryption (downgrade attacks).
Brand Identity Chain
BIMI displays your logo in email clients, but requires DMARC enforcement
DMARC Enforcement
DMARC policy: reject
→
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
Mail servers support TLS encryption
→
TLS-RPT Reporting
TLS-RPT not configured
⚠️ TLS-RPT is not configured. Without TLS reporting, you have no visibility into TLS connection failures that may be impacting email delivery.
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/offerup.com.svg" alt="Email Security Grade">
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