difu.de

Nameservers · These nameservers report their software version via version.bind/version.server, which helps attackers find known vulnerabilities: ns.difu.de: "9.20.29-1~deb13u1-Debian". Hide or replace the version string.

SOA · retry 4h should be shorter than refresh 3h. Current values: refresh 3h, retry 4h, expire 28d, negative TTL 10m.

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: A (1m). Low TTLs are useful just before a planned change.

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

DKIM · The _domainkey name exists but no DKIM key was found under the common selectors. Selectors are provider-specific; check yours with -selector.

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: a1221.mx.srv.dfn.de, b1221.mx.srv.dfn.de, c1221.mx.srv.dfn.de

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.

TLS · MTA-STS or DANE is used without TLS-RPT, so you get no reports when senders fail to deliver because of TLS problems. Publish _smtp._tls TXT "v=TLSRPTv1; rua=mailto:...".