rivm.nl

DNSSEC · NSEC3 uses 10 iterations and a 7-byte salt. RFC 9276 recommends 0 iterations and no salt: extra iterations cost resolvers CPU and add no real protection, and some validators treat high counts as insecure.

Records · These records have a TTL below 5m, causing extra queries and slower lookups: A (2m). Low TTLs are useful just before a planned change. The NS TTL at the parent is 1h and in the zone 8h; resolvers may use either.

MX · The following MX hosts could not be resolved to IPv6 addresses: externemail.rivm.nl

DKIM · 1024-bit RSA keys are the minimum and are considered weak today: selector1 (1024 bits). Rotate to a 2048-bit key.

MX · These MX addresses have no PTR record, which many receivers treat as a spam signal: 2001:610:430:ffff::17:16 (externemail-mx2.rivm.nl). Ask your hosting provider to set one.

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.