DNS Security Check: How to Audit Your Domain's DNS Configuration

Why DNS Security Matters

DNS (Domain Name System) is the backbone of how the internet finds your domain. Every time someone visits your website, sends you email, or connects to your API, DNS is involved. And because DNS was designed in the 1980s without security in mind, it's full of attack surfaces that require active protection.

A DNS security check examines your domain's DNS records to find vulnerabilities, misconfigurations, and missing protections. Think of it as a health checkup for your domain: it won't fix problems on its own, but it tells you exactly what needs attention before attackers find it first.

The stakes are real. Misconfigured email authentication means your domain can be spoofed in phishing attacks. Missing DNSSEC means attackers can poison DNS responses and redirect your visitors. Expired SSL certificates break trust and trigger browser warnings. And missing security headers leave your users vulnerable to cross-site scripting and clickjacking.

The Six Areas of a DNS Security Check

A thorough DNS security audit covers six distinct areas. Each protects against different threats, and each requires its own DNS records and configuration.

1. SPF (Sender Policy Framework)

SPF defines which mail servers are authorized to send email for your domain. It's a TXT record that lists IP addresses, includes for third-party services, and a fail mechanism (-all or ~all).

What to check: Does the record exist? Does it include all your legitimate sending services? Is it under the 10 DNS lookup limit? Does it end with -all (hard fail) rather than ~all (soft fail)? Check your SPF record →

2. DKIM (DomainKeys Identified Mail)

DKIM adds cryptographic signatures to your outgoing emails. The receiving server uses a public key in your DNS to verify the signature, confirming the message came from you and wasn't altered in transit.

What to check: Are DKIM keys published for each sending service? Are key lengths at least 2048 bits? Are there stale keys from old providers that should be removed? Check your DKIM record →

3. DMARC (Domain-based Message Authentication, Reporting & Conformance)

DMARC ties SPF and DKIM together with a policy that tells receivers what to do when authentication fails. It also enables reporting so you can see who's sending email as your domain.

What to check: Does a DMARC record exist? Is the policy stronger than p=none? Are aggregate reporting addresses configured? Is the subdomain policy set? Check your DMARC record →

4. DNSSEC (DNS Security Extensions)

DNSSEC adds cryptographic signatures to DNS responses, allowing resolvers to verify that the response actually came from the authoritative nameserver and wasn't tampered with. Without DNSSEC, attackers can perform DNS cache poisoning, redirecting your visitors to a malicious server without them knowing.

What to check: Is DNSSEC enabled on your domain? Are the DS records properly configured at your registrar? Is the chain of trust intact from root to your zone? Check your DNSSEC status →

5. SSL/TLS Certificates

SSL/TLS certificates encrypt the connection between your server and visitors' browsers. They're essential for HTTPS and are a baseline expectation for any modern website.

What to check: Is the certificate valid and not expired? Does it cover all your subdomains? Is the TLS version current (1.2 or 1.3)? Are weak cipher suites disabled? Check your SSL certificate →

6. HTTP Security Headers

Security headers are HTTP response headers that instruct browsers to enable protections against common web attacks. They're configured on your web server, not in DNS, but they're a critical part of your domain's security posture.

What to check: Is HSTS enabled (forcing HTTPS)? Is Content-Security-Policy set? Are X-Frame-Options, X-Content-Type-Options, and Referrer-Policy configured? Check your security headers →

The Most Common DNS Security Issues We Find

After scanning thousands of domains, these are the problems that come up again and again, ranked roughly by how frequently we see them:

No DMARC Record (or Stuck on p=none)

This is the single most common issue. Many domains either have no DMARC record at all, or they published p=none years ago and never progressed to enforcement. Without an enforcing DMARC policy, your domain can be freely spoofed in phishing emails. Since Google and Yahoo began requiring DMARC in 2024, this also directly affects email deliverability.

SPF Record Exceeding 10 Lookups

SPF has a hard limit of 10 DNS lookups (includes, redirects, MX, A mechanisms). When you exceed this limit, the entire SPF record fails, meaning your authenticated email looks unauthenticated. This is especially common for organizations using multiple SaaS tools that each require an SPF include.

Missing DNSSEC

DNSSEC adoption is still relatively low, but it's increasingly important. Without it, your domain is vulnerable to DNS spoofing and cache poisoning attacks. Enabling DNSSEC requires coordination between your registrar and DNS provider, which is why many domains skip it. That said, the protection it provides is worth the setup effort.

Weak or Missing Security Headers

Security headers are often overlooked because they're configured on the web server rather than in DNS. Missing HSTS means browsers don't enforce HTTPS. Missing Content-Security-Policy opens the door to XSS attacks. Missing X-Frame-Options allows clickjacking. These are quick wins that significantly improve your security posture.

Expiring or Misconfigured SSL Certificates

With Let's Encrypt and automated renewal, SSL problems are less common than they used to be, but they still happen. Certificates that don't cover all subdomains, chains with missing intermediate certificates, and wildcard certificates that aren't properly deployed all cause browser warnings that destroy user trust.

A Practical Approach to Fixing DNS Security Issues

You don't need to fix everything at once. Here's a priority order based on impact and effort:

1. Fix SPF first because it's the quickest to set up and has immediate impact on email deliverability. Add all your legitimate senders and ensure you're under 10 lookups.
2. Enable DKIM on all sending services. Most email providers make this a one-click setting plus a DNS record. It takes minutes per service.
3. Deploy DMARC with enforcement. Start at p=none, review reports, and progress to p=reject. This is the biggest single improvement for email security.
4. Add security headers. These can usually be added in a single server configuration change or via your CDN. Start with HSTS and X-Content-Type-Options.
5. Verify SSL configuration: ensure valid certificates, TLS 1.2+, and no weak cipher suites.
6. Enable DNSSEC. This requires both your DNS provider and registrar to support it. Check with both before starting.

Frequently Asked Questions

What does a DNS security check include?

A comprehensive DNS security check examines six key areas: SPF records (authorized email senders), DKIM records (email signature verification), DMARC policy (email authentication enforcement and reporting), DNSSEC (DNS response integrity), SSL/TLS certificates (encrypted connections), and HTTP security headers (browser-level protections like HSTS and CSP). Together, these cover email security, DNS integrity, and web security.

How often should I run a DNS security check?

Run a DNS security check at least quarterly, and immediately after any DNS changes: adding a new email service, changing hosting providers, updating nameservers, or renewing SSL certificates. If you're actively improving your security posture (e.g., rolling out DMARC enforcement), check weekly during the transition period.

Can DNS security issues affect email deliverability?

Yes, significantly. Missing or misconfigured SPF, DKIM, and DMARC records directly impact email deliverability. Since 2024, Google and Yahoo require DMARC for bulk senders, and without it your emails may be rate-limited, sent to spam, or rejected entirely. Even non-bulk senders benefit from proper email authentication, as major providers increasingly use it as a signal for inbox placement.

Run Your DNS Security Check Now

A complete DNS security audit shouldn't take days of manual work. Our scanner checks all six areas in seconds and gives you a prioritized list of issues with specific fixes.

→ Run a free DNS security check covering SPF, DKIM, DMARC, DNSSEC, SSL, and security headers in one scan.

Or use our individual tools to deep-dive into specific areas: SPF Checker · DKIM Checker · DMARC Checker · DNSSEC Checker · SSL Checker · Security Headers Checker