Comparison
MXToolbox built its reputation on fast DNS lookups and blacklist checks. ZeroHook is built for teams that need those problems fixed continuously — with 35 audit checks, provider-specific DNS remediation, and compliance evidence when auditors ask for proof.
Best for SMB IT admins, MSPs, and marketing ops teams who send mail through M365, Google Workspace, or ESPs and need ongoing SPF/DKIM/DMARC monitoring — not just a one-off lookup when something breaks.
MXToolbox is one of the most recognized names in DNS diagnostics. Its free lookup tools are excellent for answering “what does this TXT record say right now?” and its paid monitoring plans alert you when records change or blacklists list your IPs. For many admins, that workflow is enough for reactive troubleshooting.
The gap appears when mail still lands in spam after SPF passes, when DMARC aggregate reports show alignment failures you cannot map to a fix, or when a client audit asks for continuous evidence that email authentication was monitored — not just spot-checked. MXToolbox shows the data; ZeroHook tells you what to change in Cloudflare, Route53, or M365 and tracks whether the fix held.
ZeroHook runs 35 audit checks per domain: authentication (SPF, DKIM, DMARC, MTA-STS, BIMI), infrastructure (CAA, DNSSEC, dangling records), reputation (blacklists), and compliance mapping (NIS2, SOC2 CC6.6, ISO 27001 Annex A). Paid tiers add continuous monitoring with configurable cadence, unlimited manual re-scans, and on the Evidence tier, tamper-proof logs exportable for auditors.
Choose ZeroHook when your primary pain is deliverability, authentication rollout, or compliance evidence — not just DNS lookups.
SPF can pass while DMARC fails alignment, or DKIM may be missing on your ESP path. ZeroHook surfaces all 35 failure modes — including the ones Gmail and Microsoft bulk-sender rules care about in 2026 — and links each finding to a copy-paste fix for your DNS provider.
Agency tier ($89/mo) and white-label ($15/domain) let you monitor client portfolios under your brand, export bulk CSV reports, and bill monitoring as a managed service. MXToolbox partner programs exist but are not built around email-auth remediation at SMB price points.
Evidence tier ($199/mo) stores 365 days of hash-verified audit history, generates auditor PDFs, and offers read-only portal access. MXToolbox monitoring alerts on changes; it does not produce NIS2 or SOC2 evidence packs.
ZeroHook is the only tool in this price range that outputs provider-specific DNS records — e.g. the exact SPF include for Mailchimp on Cloudflare, or the DKIM CNAME for Google Workspace on Route53. That cuts rollout time from hours of documentation hunting to minutes of copy-paste.
MXToolbox remains a strong choice in specific scenarios. A factual comparison does not mean replacing every workflow.
If your daily work is “check this IP on Spamhaus” or “test this MX host,” MXToolbox’s lookup UX is mature and fast. ZeroHook includes blacklist checks inside the 35-check audit but is optimized for domain-level authentication monitoring, not pen-test-style SMTP probes.
MXToolbox sells broader network monitoring (uptime, ports, etc.) in the same ecosystem. If you already pay for that bundle and only need occasional SPF lookups, adding ZeroHook for email-auth depth may be complementary rather than a full swap.
Free MXToolbox lookups plus ZeroHook’s free SPF/DMARC checkers can coexist at zero cost. Upgrade to ZeroHook paid when you need continuous monitoring or when a Gmail 550 error blocks production mail.
MXToolbox pricing depends on product bundle (SuperTool, Monitoring, Delivery Center). Public list prices trend higher than ZeroHook Deliverability for comparable domain counts. ZeroHook includes unlimited manual audits on all paid tiers.
Deliverability $29/mo · Agency $89/mo · Evidence $199/mo
~$129/mo (~$1,548/yr for SuperTool monitoring bundles)
Fact-based comparison from public product positioning. Verify competitor details on their site before purchase decisions.
| Feature | ZeroHook | MXToolbox |
|---|---|---|
| Primary focus | Email authentication + DNS security + compliance evidence | DNS diagnostics, blacklist checks, uptime monitoring |
| Audit depth | 35 checks (SPF, DKIM, DMARC, MTA-STS, BIMI, typosquatting, and more) | Individual lookup tools; depth depends on subscription tier |
| Copy-paste DNS fixes | Yes — provider-specific (Cloudflare, Route53, M365, etc.) | No — shows results; you write records manually |
| Continuous monitoring | Yes — configurable cadence on paid tiers | Yes — on paid monitoring plans |
| Compliance evidence (NIS2, SOC2) | Evidence tier: tamper-proof logs, auditor PDFs, Excel export | Not a compliance evidence platform |
| MSP / white-label | Agency tier + white-label from $15/domain | Partner programs available; different positioning |
| Free tools | DNS visualizer, SPF/DMARC/MTA-STS checkers (no account) | Free single lookups with usage limits |
Export your current domain list from MXToolbox (or your client spreadsheet) and add each domain in ZeroHook — start with a free scan on the homepage to baseline scores.
Run a full 35-check audit on paid tier; compare findings to your last MXToolbox alert history. Focus first on DMARC alignment and missing DKIM — the top causes of spam-folder placement in 2026.
Apply copy-paste fixes from ZeroHook remediation panel; re-scan to confirm. Disable overlapping MXToolbox email-auth alerts only after 48 hours of clean monitoring to avoid alert gaps.
For MSPs: enable white-label branding before client-facing reports; set monitoring cadence per SLA (daily for production mail domains, weekly for parked domains).
For teams whose main need is email authentication monitoring, DMARC rollout, and compliance evidence, ZeroHook replaces the MXToolbox monitoring workflow with deeper audit checks and copy-paste fixes. MXToolbox remains useful for ad-hoc blacklist and DNS lookups.
Yes. ZeroHook audit checks include blacklist and reputation signals as part of the 35-check scan, alongside SPF, DKIM, DMARC, and infrastructure checks.
ZeroHook Deliverability at $29/mo covers continuous monitoring for one domain with add-on pricing for extras. MXToolbox monitoring bundles are typically higher annually for comparable continuous coverage.
Yes. Agency and white-label tiers let MSPs monitor client domains under their brand with bulk export and margin-friendly per-domain pricing.
Most SMBs standardize on ZeroHook for monitoring and fixes. Keep MXToolbox if you rely on its specific one-off lookup UX — ZeroHook free tools cover SPF, DMARC, and DNS visualization without an account.
Most teams baseline all domains in one session, apply fixes over 1–2 weeks as DNS propagates, and fully transition alerts within 30 days. DMARC p=none monitoring should run at least 14 days before tightening policy.
Gmail and Microsoft spam-folder legitimate mail for authentication, DNS, reputation, and list-hygiene reasons most admins never audit. All 35 failure modes and fixes in one guide.
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The 550 5.7.26 authentication required bounce means Gmail rejected your message before inbox placement. Fix SPF, DKIM, DMARC alignment, and envelope-from settings for M365 and Google Workspace.
