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Feature checklists make every tool look equivalent. This table leads with the three things that actually differ — what it costs you before it works, whether your files leave your device, and where the free version stops.
| MXToolboxmxtoolbox.com | Formspreeformspree.io | Google Admin Toolbox Messageheadertoolbox.googleapps.com | Mail-Testermail-tester.com | |
|---|---|---|---|---|
| What it does | Looks up MX, SPF, DKIM and DMARC records and names the one that is wrong | Gives a static site's contact form somewhere to POST that emails you the answers | Paste raw email headers and see every hop, the delay at each, and the auth results | Send one email to the address it gives you and get a spam score out of ten |
| What it costs you | Free tierA genuinely usable free tier with paid plans for volume or team features. | Free tierA genuinely usable free tier with paid plans for volume or team features. | No sign-upWorks the moment the page loads. No account, no email, no trial. | Free tierA genuinely usable free tier with paid plans for volume or team features. |
| Your files | Runs on their server | Runs on their server | Runs on their server | Runs on their server |
| Where it stops | Anonymous lookups are rate-limited, and monitoring, alerting and bulk checks all need a paid account. | Free takes 50 submissions a month across all your forms and keeps only 30 days of history. | It reads what the headers claim and nothing more — it cannot tell you a message was spam, only that the authentication passed or failed. | Three tests per 24 hours from one address, and the score grades your configuration rather than predicting real inbox placement. |
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| Category | Email & Communication | Email & Communication | Email & Communication | Email & Communication |
| Last checked | 2026-07-29 | 2026-07-29 | 2026-07-29 | 2026-07-29 |
| Open the site | Open | Open | Open | Open |
This comparison is in the address bar — copy the URL to send it to someone.