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monzo.com

Name: monzo.com Email Security Posture Assessment
Creator: RacterMX

Posture Score: 84/100

Scanned May 8, 2026 at 4:55 PM UTC

Identity

Attack Surface

Reputation

100

Identity Findings

Weak DKIM RSA key (~1296 bits) for selector 's2'

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.

high

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.monzo.com/.well-known/mta-sts.txt

medium

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.

medium

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@monzo.com").

low

Very low TTL on MX records: 282s

5 MX records have a TTL of 282s or less (below 300s).

💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.

low

Very low TTL on A records: 42s

4 A records have a TTL of 42s or less (below 300s).

💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.

low

Very low TTL on TXT records: 282s

29 TXT records have a TTL of 282s or less (below 300s).

💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.

low

Very low TTL on SPF record: 282s

The SPF record has a TTL of 282s or less (below 300s).

💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.

low

Very low TTL on DMARC record: 282s

The DMARC record has a TTL of 282s or less (below 300s).

💡 Increase the TTL to at least 300 seconds unless frequent changes are expected.

low

NS TTL mismatch between parent and authoritative zone

The NS record TTL in the parent zone (~7182s) differs significantly from the authoritative zone (~86400s).

💡 Align NS record TTLs between the parent zone delegation and the authoritative zone.

low

SPF record is valid

The SPF record is properly configured with valid syntax and within lookup limits.

pass

DKIM cryptographic configuration is compliant

No RFC 8301 compliance issues detected in DKIM key configuration.

pass

BIMI record is valid

BIMI is properly configured with a valid logo and DMARC enforcement.

pass

ARC support likely available

MX server software appears to support ARC headers for authentication preservation.

pass

SMTP security checks passed

No open relay, VRFY/EXPN, or banner disclosure issues detected.

pass

SMTP RFC 5321 compliance checks passed

The mail server accepts postmaster@ and abuse@ and uses a valid FQDN in EHLO.

pass

IPv6 readiness is good

IPv6 records are present and properly configured.

pass

NS delegation is properly configured

All nameservers are responsive, consistent, and properly secured.

pass

DNS responses are consistent across all nameservers

All authoritative nameservers return consistent answers with proper AA flags.

pass

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.

informational

DMARC alignment: adkim=r, aspf=r

DKIM alignment is relaxed, SPF alignment is relaxed.

informational

DMARC failure reporting: fo=1

Failure reports generated when any authentication mechanism fails.

informational

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.

informational

Deprecated DMARCbis tags found: pct

The DMARC record contains tags deprecated in DMARCbis: pct. Consider removing these for forward compatibility.

informational

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.

informational

Shared/free email hosting detected: aspmx.l.google.com

The MX record points to a known shared or free email hosting provider.

informational

Shared/free email hosting detected: alt1.aspmx.l.google.com

The MX record points to a known shared or free email hosting provider.

informational

Shared/free email hosting detected: alt2.aspmx.l.google.com

The MX record points to a known shared or free email hosting provider.

informational

Shared/free email hosting detected: alt3.aspmx.l.google.com

The MX record points to a known shared or free email hosting provider.

informational

Shared/free email hosting detected: alt4.aspmx.l.google.com

The MX record points to a known shared or free email hosting provider.

informational

No DANE/TLSA records found

DANE is not configured for any MX server. This is optional but provides strong certificate binding.

informational

Open mail ports on aspmx.l.google.com

Detected open mail-related ports: 25

informational

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.

informational

MX IP network diversity

MX IPs span 5 different /16 networks, providing good diversity.

informational

SOA record parameters

Serial: 2402895673, Refresh: 10000s, Retry: 2400s, Expire: 604800s, Min TTL: 1800s

informational

Authorized certificate authorities

CAA records restrict certificate issuance to: amazon.com, buypass.com, comodoca.com, digicert.com; cansignhttpexchanges=yes, letsencrypt.org, pki.goog; cansignhttpexchanges=yes, ssl.com

informational

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.

high

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.

high

Internal information in TXT record

A TXT record for monzo.com contains references to internal resources: internal.monzo.com, login.internal

💡 Remove internal hostnames and IP addresses from public TXT records.

medium

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.

medium

No email autodiscovery endpoints detected

No Microsoft Autodiscover, Mozilla Autoconfig, or email SRV records were found.

pass

7 subdomain(s) discovered for monzo.com

Subdomains were enumerated via Certificate Transparency logs, DNS wordlist brute-forcing, and DNS record analysis.

informational

0 certificate(s) found in CT logs

Certificate Transparency logs contain 0 certificate(s) for monzo.com and its subdomains. Each certificate reveals subdomain names.

informational

DNSSEC is enabled

DNSKEY and/or DS records are present, indicating DNSSEC is configured.

informational

Reputation Findings

HSTS enabled with preload on monzo.com

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

pass

security.txt present

Found security.txt at https://monzo.com/.well-known/security.txt.

pass

TLS certificate valid for 295 days

Certificate for monzo.com expires on 2027-02-27.

pass

Certificate issued by Amazon RSA 2048 M04

The certificate for monzo.com is issued by a third-party CA.

pass

Signature algorithm: rsa-sha256

The certificate for monzo.com uses an acceptable signature algorithm.

pass

RSA key: 2048 bits

The certificate for monzo.com uses an adequate RSA key of 2048 bits.

pass

SCTs present in certificate

The certificate for monzo.com contains Signed Certificate Timestamps.

pass

No weak ciphers detected

No known weak cipher suites detected on monzo.com.

pass

Domain valid for 247 days

Domain monzo.com expires on 2027-01-11.

pass

Domain transfer and delete locks enabled

Domain monzo.com has clientTransferProhibited and clientDeleteProhibited locks.

pass

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.

informational

Abuse contact lookup failed

Could not query abuse contact information.

informational

PhishTank — API key required

PhishTank phishing database check requires an API key.

informational

Sender Score — API key required

Sender Score reputation check requires an API key.

informational

Cisco Talos — API key required

Cisco Talos IP reputation check requires an API key.

informational

Could not connect to webmail.monzo.com

HTTPS request to https://webmail.monzo.com failed or timed out.

informational

WHOIS registration data

Registrar: Amazon Registrar, Inc. | Created: 1998-01-19 | Expires: 2027-01-11 | Updated: 2023-01-13

informational

WHOIS privacy protection not detected

Domain monzo.com does not appear to have WHOIS privacy protection. Registrant details may be publicly visible.

informational

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: aspmx.l.google.com

PTR record proves mail server legitimacy

MX: aspmx.l.google.com Mail server at 74.125.193.26 → PTR Record Reverse DNS: di-in-f26.1e100.net

Mail Server Identity: alt1.aspmx.l.google.com

PTR record proves mail server legitimacy

MX: alt1.aspmx.l.google.com Mail server at 173.194.76.27 → PTR Record Reverse DNS: ws-in-f27.1e100.net

Mail Server Identity: alt2.aspmx.l.google.com

PTR record proves mail server legitimacy

MX: alt2.aspmx.l.google.com Mail server at 142.250.102.27 → PTR Record Reverse DNS: rb-in-f27.1e100.net

Mail Server Identity: alt3.aspmx.l.google.com

PTR record proves mail server legitimacy

MX: alt3.aspmx.l.google.com Mail server at 192.178.213.26 → PTR Record Reverse DNS: yugrqzs-in-f26.1e100.net

Mail Server Identity: alt4.aspmx.l.google.com

PTR record proves mail server legitimacy

MX: alt4.aspmx.l.google.com Mail server at 142.251.127.26 → PTR Record Reverse DNS: lcfrai-in-f26.1e100.net

Mail Server Reputation: aspmx.l.google.com