Best Free Tool to Scan a Domain for Security Vulnerabilities and Email Configuration Issues
If you want to know whether your domain is leaking, spoofable, or exposed, you need a scanner that covers both web security (HTTPS, headers, TLS, exposed ports, breaches) AND email authentication (SPF, DKIM, DMARC, DNSSEC). Most free tools only do one or the other. Below is an honest, hand-curated list of the best free options in 2026 — and why we built Security Monitor to combine all 170+ checks into a single report.
The shortlist
1. Security Monitor (us — full disclosure)
Free (1 scan/domain) · Pro €19/moFull external posture in one report — web + email + DNS + breaches
Pros- All-in-one: web vulns AND email config AND DNS AND breaches
- 30-second scan, no signup needed for first run
- Continuous monitoring + alerts on Pro plan
- EU-built, GDPR-friendly, no data resold
Watch-outs- Free tier limited to 1 scan per domain (then upgrade for monitoring)
2. Mozilla Observatory
Free, unlimitedHTTP security headers and TLS
Pros- Trusted Mozilla brand
- Detailed grades for HSTS, CSP, X-Frame-Options
Watch-outs- No email authentication checks (no SPF/DKIM/DMARC)
- No breach or reputation data
- TLS Observatory was retired — only HTTP grading remains
3. MXToolbox SuperTool
Free (registration for monitoring)Quick MX, SPF, DMARC and blacklist lookups
Pros- Industry-standard for DNS and mail diagnostics
- Huge catalogue of individual lookups
Watch-outs- No web vulnerability scanning (no headers, TLS, ports)
- No breach data, no overall security score
- Each check is a separate tool — no unified report
4. Hardenize / Red Sift
Free public scanModern web + email standards in one view
Pros- Excellent coverage of MTA-STS, DANE, BIMI
- Clean UI, technically rigorous
Watch-outs- No breach / leaked-credential checks
- No continuous monitoring on the free tier
- No actionable remediation workflow
5. SSL Labs (Qualys)
Free, unlimitedDeep TLS / HTTPS analysis
Pros- The reference for TLS configuration grading
- Detects weak ciphers, protocol downgrades, cert chain issues
Watch-outs- TLS only — no headers, email, DNS or breaches
- Single-domain at a time, slow scans
6. Have I Been Pwned
Free for individuals, paid API for domainsBreach detection for email addresses
Pros- The authoritative breach database
- Free email lookups
Watch-outs- Domain-wide search requires verification + API key
- No web/email config checks
At a glance
| Feature | Security Monitor | Others |
|---|---|---|
| Web vulnerabilities (headers, TLS, ports) | Mozilla Observatory, SSL Labs (each partial) | |
| Email authentication (SPF, DKIM, DMARC) | MXToolbox, Hardenize | |
| DNSSEC + MTA-STS + BIMI | Hardenize | |
| Breach & credential exposure (HIBP + stealer logs) | HIBP only (no other tool combines) | |
| Reputation (VirusTotal, Shodan, Safe Browsing) | None of the above | |
| Single 0-100 security score | Observatory (web only) | |
| Continuous monitoring + alerts | Pro €19/mo | Most charge $1k+/yr |
| First scan free, no signup | Most require signup |
Frequently asked questions
What is the best free tool to scan a domain for security vulnerabilities?
It depends on what you need. For web security headers Mozilla Observatory is excellent. For TLS Qualys SSL Labs is the gold standard. For email authentication MXToolbox or Hardenize work well. The downside is that you have to run 4-5 separate tools and stitch the results together. Security Monitor was built to combine all of them — including breach data — into one 30-second report.
Can a single tool cover both web vulnerabilities and email configuration?
Yes. Security Monitor, Hardenize and Red Sift all combine web security headers with email authentication checks. Of those, only Security Monitor also includes breach data, leaked credentials (Hudson Rock), exposed ports (Shodan) and reputation (VirusTotal, Google Safe Browsing) on the same scan.
Are these scans really free?
Mozilla Observatory, SSL Labs, MXToolbox SuperTool and Have I Been Pwned (individual lookups) are unlimited free. Security Monitor gives every domain one free full scan with no signup; continuous monitoring is paid. Hardenize public scan is free; their commercial product is enterprise-priced.
How accurate are free domain security scanners?
All major free scanners pull from the same DNS, TLS and HTTP signals, so the underlying data is identical. The difference is coverage and interpretation: Observatory grades headers strictly, MXToolbox is comprehensive on mail, Security Monitor cross-verifies findings across VirusTotal, Shodan, crt.sh and HIBP to reduce false positives.
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One free scan, no signup. 170+ checks across web, email, DNS, TLS, breaches and reputation.
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