groningen.nl

Delegation · The addresses at the parent (glue) differ from the addresses in the zone: ns1.qsp.nl (glue 193.254.215.240, zone 193.254.215.240, 2a04:c580:0:f0::1); ns2.qsp.nl (glue 193.254.215.241, zone 193.254.215.241, 2a04:c580:0:f1::1). Update the glue at your registrar.

Delegation · all IPv4 addresses are in 193.254.215.0/24; all IPv6 addresses are in 2a04:c580::/48. A single network failure takes all nameservers down; RFC 2182 recommends topologically separate networks (anycast setups are an exception).

SOA · retry 1h should be shorter than refresh 1h. Current values: refresh 1h, retry 1h, expire 7d, negative TTL 1h.

DNSSEC · NSEC3 uses 33 iterations and a 8-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.

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

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:...".