You just checked a blacklist on MXToolbox, and now you're wondering whether that is enough. MXToolbox has been around since 2003 and is one of the most widely used free tools for email administrators and IT teams. If you've ever checked a blacklist, looked up an MX record, or verified SPF syntax, you've probably used it.
Brain is a different kind of product. Rather than running one-off lookups, it watches your sending around the clock and diagnoses a drop when it happens. The comparison isn't really "which is better" — it's "which does the job you actually need done."
What MXToolbox does well
MXToolbox excels as an on-demand diagnostic utility. Its core strengths:
- Blacklist checking — quick check whether an IP or domain is listed on any of 100+ blacklists. Free, fast, comprehensive.
- DNS record lookup — inspect MX, SPF, DKIM, DMARC, PTR, and A records in a clear interface. Invaluable when your SPF, DKIM or DMARC setup is misbehaving.
- MX record health — verify mail server configuration and catch common misconfigurations.
- SMTP diagnostics — test SMTP connectivity, banner checks, and TLS support.
- A snapshot score — the paid MXToolbox Deliverability product gives a one-time score with recommendations.
For IT teams setting up email infrastructure, troubleshooting a one-off issue, or verifying configuration after a DNS change, MXToolbox is a solid pick. It's free for basic lookups and the paid plans are reasonably priced.
Where Brain goes further
MXToolbox shows you the state of your setup at the moment you run a check. Brain watches it around the clock and reacts when something changes.
What Brain does that MXToolbox doesn't:
- Always watching — 30+ data points tracked at once across Gmail, Outlook, and Yahoo, no manual action required.
- Live domain health — how Gmail and Outlook score you, from Google Postmaster, Microsoft SNDS, and Sender Score, pulled continuously rather than on demand.
- Incidents raised on their own — the alert system opens an incident the moment a number drifts from its baseline.
- The cause, not just the symptom — the RCA Inspector and the diagnosis engine trace why the drop happened, not just that it happened.
- Pattern recognition — recurring failure signatures across incidents, surfaced for permanent fixes.
- Fix tracking — Outcome Tracker confirms whether a fix worked by watching the numbers recover.
Feature comparison
| Feature | InboxStack Brain | MXToolbox |
|---|---|---|
| Primary function | Watches your sending 24/7 | On-demand DNS & email diagnostics |
| How it watches | Real-time 24/7 automated | Manual checks only |
| Automated alerts | Yes — the alert system raises incidents | Limited — paid-plan alerts |
| Finding the cause | Yes — the diagnosis engine + RCA Inspector | No |
| How Gmail and Outlook score you | Continuous Postmaster, SNDS, Sender Score | Snapshot in the Deliverability product |
| SPF, DKIM, DMARC checks | Ongoing pass rates and record health | On-demand DNS lookups |
| Blacklist checks | Continuous across major RBLs | On-demand 100+ blacklists (free) |
| MBP coverage | Gmail, Outlook, Yahoo — live data | Generic — not MBP-specific |
| Incident management | War Room, Resolution Center | No |
| Free DNS lookups | Free DNS Checker for ad-hoc use | Yes — excellent free tool |
| Pricing | Free 30-day trial — talk to us for a plan | Free basic / paid from ~$129/month |
| Best for | Senders who need to know before a client does | IT teams doing one-off DNS diagnostics |
Pricing
MXToolbox's free tier covers basic lookups and is genuinely useful without spending anything. The paid Deliverability plans start around $129/month and add alerts, scoring, and additional checks.
Brain starts with a free 30-day trial — full access to live watching, the alert system, RCA Inspector, and Resolution Center, no credit card. After the trial, plans are sized to your sending volume, connectors, and domains. Talk to us →
Which one do you need?
Use MXToolbox if you need to:
- Quickly check whether an IP is blacklisted
- Look up and validate DNS records (MX, SPF, DKIM, DMARC, PTR)
- Troubleshoot a one-off mail server configuration issue
- Test SMTP connectivity to a mail server
- Run a free email infrastructure health check
Use Brain if you need to:
- Know when your inbox rate is slipping — before your recipients tell you
- Understand why your inbox rate dropped, not just that it did
- Watch multiple domains across Gmail, Outlook, and Yahoo around the clock
- Work through spam-folder incidents with a team, in one place
- Confirm that a fix actually resolved the underlying problem
The verdict
MXToolbox is a valuable free tool for one-off DNS diagnostics and blacklist checks — it has earned its place in every email administrator's bookmarks. Brain solves a different problem: it watches your sending around the clock and catches a drop before it costs you the inbox. For teams that send at volume and can't afford to hear about a spam-folder problem after the fact, Brain is what you need.
Still weighing options? Read the full buyer's guide →