crous-lyon.fr

Delegation · all IPv4 addresses are in 193.55.52.0/24. A single network failure takes all nameservers down; RFC 2182 recommends topologically separate networks (anycast setups are an exception).

Delegation · None of the nameservers has an IPv6 address, so IPv6-only resolvers can't reach them.

Nameservers · These nameservers report their software version via version.bind/version.server, which helps attackers find known vulnerabilities: ns1.crous-lyon.fr: "9.20.29-1~deb13u1-Debian"; ns2.crous-lyon.fr: "9.20.29-1~deb13u1-Debian". Hide or replace the version string.

SOA · retry 1h should be shorter than refresh 1h. Current values: refresh 1h, retry 1h, expire 700d, negative TTL 1h.

DNSSEC · The zone is not signed with DNSSEC, so answers can be spoofed. Enable DNSSEC at your DNS provider and publish the DS record at your registrar.

Records · These records have a TTL below 5m, causing extra queries and slower lookups: MX (0s). Low TTLs are useful just before a planned change.

SPF · SPF record needs 6 DNS lookups (limit is 10). Problems found: include:spf.mailing.crous-rouen.fr does not exist or has no records.

DMARC · DMARC policy is set to 'quarantine'. Consider upgrading to 'reject' for stronger protection once you've verified legitimate emails are passing authentication.

DNSSEC · DNSSEC is not enabled for this domain. Consider enabling DNSSEC to protect against DNS spoofing attacks.

MX · The following MX hosts could not be resolved to IPv6 addresses: mx1.relay.renater.fr, mx2.relay.renater.fr

SPF · 1 include/redirect target does not exist or has no records (limit is 2). This usually is a stale include; remove it.

TLS · MTA-STS is not configured, so other mail servers fall back to unencrypted delivery when TLS fails or is stripped by an attacker. Publish a _mta-sts TXT record and a policy at https://mta-sts.<domain>/.well-known/mta-sts.txt.