Quick answer
Free Mail Tester - For most builders, Free Mail Tester wins because it covers a broader deliverability check workflow with unlimited no-signup testing, while DKIMValidator is better only if you specifically want a simpler DKIM/SPF-focused rerun tool.
How the free tiers compare
These two free tiers solve overlapping but different problems. DKIMValidator is a narrow validation utility: send mail to an @dkimvalidator.com address, then inspect DKIM, SPF, SpamAssassin, and related results, with the useful extra of re-testing the same saved message after DNS changes. Free Mail Tester is wider in scope: it generates a unique test address, scores inbox placement and spam signals, and checks a longer list of deliverability signals including DMARC alignment, reverse DNS, blacklist status, TLS, headers, and HELO/EHLO matching. The tradeoff is depth versus breadth. DKIMValidator is good when you are debugging a specific authentication issue and want to re-check after fixes. Free Mail Tester is better when you want a more complete pre-send or campaign sanity check, and its free tier is explicitly unlimited with no signup or card required.
DKIMValidator.com vs Free Mail Tester free tier, side by side
| DKIMValidator.comFTV 90 | Free Mail TesterFTV 49 | |
|---|---|---|
| Free usageB explicitly says no monthly cap and no signup required. | Always free, no stated cap | Unlimited free email deliverability tests |
| Message retentionA saves the message briefly so you can retest it. | A few hours before deletion | Not stated |
| Re-testing after DNS changesA explicitly supports repeated re-testing of the same saved message. | Included | Not stated |
| Checks includedB’s checklist is broader; A is more focused. | DKIM, SPF, SpamAssassin, DomainKeys | SPF, DKIM, DMARC alignment, Rspamd, reverse DNS, blacklist status, content, links, TLS, headers, HELO/EHLO |
After you outgrow the free tier
Neither tool has a paid tier. DKIMValidator has no paid plan, and the Free Mail Tester deliverability test at this URL is unlimited and free with no credit packs or subscription of any kind. Both stay free at any usage volume.
Cost at real usage
| Usage | DKIMValidator.com | Free Mail Tester |
|---|---|---|
| 5,000 validation testsNeither tool charges for this volume. | Free | Free |
| 25,000 validation testsFree Mail Tester has no usage cap on its deliverability test. | Free | Free |
| 100,000 validation testsFree Mail Tester has no usage cap on its deliverability test. | Free | Free |
| 250,000 validation testsNeither tool has a paid gate. | Free | Free |
Estimates, not quotes. Usage-based rates change - verify with the vendor's pricing page before committing.
When to pick each one
Pick DKIMValidator.com when…
- You are debugging DKIM or SPF on a single message and want to re-test the same email after DNS changes.
- You want a lightweight public tool that stores one message briefly and shows authentication and SpamAssassin results in one place.
- You are validating how a specific inbound message looks to receivers, not running a broad checklist.
- You do not need a broader inbox placement score or campaign-style deliverability analysis.
Pick Free Mail Tester when…
- You want a broader deliverability checklist, including DMARC alignment, reverse DNS, blacklist status, TLS, and HELO/EHLO matching.
- You prefer an unlimited free tier with no signup and no credit card.
- You are testing messages from a real mail client or campaign tool and want a 0 to 100 score plus analysis.
- You want a unique test address workflow for repeated pre-send checks across different campaigns.
Bottom line
If you need a broader deliverability check, Free Mail Tester is the better default because it is unlimited, no-signup, and covers more of the things that actually break inbox placement. If your job is specifically to confirm DKIM and SPF on a message and then re-test after DNS changes, DKIMValidator is the more focused tool. For most builders, B is the more useful free tier, while A is the better specialist when authentication debugging is the main task.
Read the full listings: DKIMValidator.com and Free Mail Tester. Scores use the FTV methodology at /ftv. Browse more head-to-heads on /compare, or see the top-ranked free tiers on /top.