Email Infrastructure // Online

Domain Health Checker.

A domain health checker runs a comprehensive scan of your email infrastructure in one click, testing SPF, DKIM, DMARC, and MX records alongside 50+ email blacklists. The result is a 0-100 health score with a letter grade from A to F, showing exactly where your configuration is strong and where points are lost. Each category is weighted by its impact on deliverability, and recommendations are sorted by potential score gain so you know which fixes to prioritize. It is the fastest way to diagnose why emails are landing in spam or being rejected.

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Checks SPF, DKIM, DMARC, MX records, and 50+ blacklists simultaneously.
How to Use

Get Started in 3 Steps

Step 01

Enter Your Domain

Type any domain name (e.g., example.com). The tool also accepts full URLs and email addresses, automatically extracting the domain.

Step 02

Review Your Health Score

Get a 0-100 health score with letter grade (A-F) calculated from five categories: SPF, DKIM, DMARC, MX records, and blacklist status. See exactly where points are lost.

Step 03

Follow Prioritized Fixes

Act on the recommendations sorted by score impact. Each recommendation shows the category and potential point gain, so you know which fixes will have the biggest effect.

How It Works

Under the Hood

When you submit a domain, the tool fires two API calls in parallel: one to check DNS authentication records (SPF, DKIM, DMARC, MX) and one to scan 50+ DNS-based blacklists. Both run simultaneously — each completes independently, so you see DNS results as soon as they arrive even if the blacklist scan is still running.

The DNS check queries Google DNS-over-HTTPS for TXT, CNAME, and MX records. SPF records are parsed for mechanisms, lookup counts, and qualifier analysis. DKIM probes 13 common selectors (google, default, selector1, selector2, k1, s1, s2, etc.). DMARC records are parsed for policy, reporting URIs, alignment modes, and percentage.

The blacklist check resolves the domain's MX hostnames to IP addresses and checks those IPs against IP-based DNSBLs (Spamhaus SBL/XBL, Barracuda, SpamCop, SORBS, etc.), while simultaneously checking the domain itself against domain/URL-based blacklists (Spamhaus DBL, SURBL, URIBL). All queries use a 5-second per-list timeout with a 10-second overall budget.

Once both calls complete, the deterministic scoring rubric calculates a 0-100 health score across five weighted categories. Recommendations are aggregated from all checks and sorted by potential score impact (highest point gain first), giving you a clear priority order for fixes.

FAQ

Frequently Asked Questions

What is a domain health check and why does it matter for email deliverability?
A domain health check is a comprehensive scan of your domain's email authentication records (SPF, DKIM, DMARC), mail server configuration (MX records), and blacklist status across 50+ DNSBLs. These five factors together determine whether your emails reach the inbox or land in spam. Mailbox providers like Google and Microsoft evaluate all of these signals when deciding whether to accept, filter, or reject your messages. A single misconfigured record or blacklist listing can cause deliverability to drop below 50%.
How is the domain health score calculated?
The score uses a deterministic 100-point rubric across five categories: SPF (20 points for a valid record, partial credit for issues like +all or excessive lookups), DKIM (20 points for valid signing with 2048-bit keys, reduced for test mode or weak keys), DMARC (20 points for p=reject, scaled down for quarantine or none), MX (15 points for redundant mail servers, 10 for a single server), and Blacklist (25 points for clean status, reduced for warning-severity listings, heavily penalized for critical listings). The letter grade maps to: A (90-100), B (75-89), C (60-74), D (40-59), F (below 40).
What does each letter grade mean for my email deliverability?
Grade A (90-100) means your domain has excellent email infrastructure with proper authentication, redundant mail servers, and clean blacklist status — expect 95%+ inbox placement. Grade B (75-89) indicates good setup with minor improvements needed, like adding a backup MX server or upgrading DMARC from quarantine to reject. Grade C (60-74) suggests significant gaps that are likely impacting deliverability, such as missing DKIM or a permissive DMARC policy. Grade D (40-59) means critical issues need immediate attention — you may be missing SPF or DMARC entirely. Grade F (below 40) indicates severe infrastructure problems that are almost certainly causing widespread delivery failures.
How does the blacklist check work for domain lookups?
For domain inputs, the checker runs two parallel scans. First, it queries domain-specific blacklists like Spamhaus DBL, SURBL, and URIBL that track domains found in spam content regardless of sending IP. Second, it resolves your domain's MX records to find your mail server hostnames, resolves those hostnames to IP addresses, and checks each IP against all IP-based blacklists (Spamhaus SBL/XBL, Barracuda, SpamCop, etc.). This two-pronged approach catches both domain-level and IP-level reputation issues. If MX records cannot be resolved, the IP-based check reports "unavailable" rather than penalizing the score.
What should I fix first based on my domain health results?
The recommendations section is sorted by score impact, so start from the top. In general, the highest-impact fixes are: (1) adding missing SPF, DKIM, or DMARC records — each is worth up to 20 points, (2) resolving critical blacklist listings which affect up to 25 points, (3) upgrading DMARC policy from none to quarantine or reject, (4) fixing SPF issues like +all qualifiers or exceeding the 10-lookup limit, and (5) adding backup MX servers for redundancy. Most DNS record changes take effect within 1-4 hours depending on TTL values.
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