leiden.nl

SOA · negative caching TTL (minimum) 30s is outside 5m–1d (RFC 2308 recommends 1–3 hours). Current values: refresh 4h, retry 1h, expire 14d, negative TTL 30s.

DNSSEC · The earliest signature expires at 2026-10-23 16:49 UTC (in 43h0m0s). Check that automatic re-signing works.

DNSSEC · NSEC3 uses 0 iterations and a 1-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 (30s), AAAA (30s), MX (30s), NS (30s). Low TTLs are useful just before a planned change. The NS TTL at the parent is 1h and in the zone 30s; resolvers may use either.

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

MX · Only one MX record found. For better email reliability, consider adding at least one backup MX server.

DNSSEC · DNSKEY signatures expire at 2026-10-23T16:49:58Z (in 43h0m0s). Check that re-signing works.

DKIM · 1024-bit RSA keys are the minimum and are considered weak today: selector1 (1024 bits), selector2 (1024 bits), s2 (1024 bits). Rotate to a 2048-bit key.

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:...".