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 |
| Credit card requiredFor A, the field is present and false, so a card is required. | No card requirement stated | No credit card |
| 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
DKIMValidator has no paid tier listed, so there is no upgrade path to price out. Free Mail Tester uses one-time flat credit packs rather than subscriptions, starting at $9 for 5,000 credits and scaling down in unit cost as volume rises. That means B gets cheaper per test as you buy more, while A simply stays free for the use case it supports. For small teams doing occasional deliverability checks, B’s free tier and low-entry packs are the clearer path; for ongoing DKIM/SPF debugging, A remains the cheaper option because there is no paid gate shown.
Cost at real usage
| Usage | DKIMValidator.com | Free Mail Tester |
|---|---|---|
| 5,000 validation testsB sells credits that never expire, so monthly cost is best treated as an equivalent estimate. | Free | $9/mo est. one-time purchase |
| 25,000 validation testsB’s next tier lowers the per-email cost. | Free | $29/mo est. one-time purchase |
| 100,000 validation testsB’s 100k pack is listed at $79 one time. | Free | $79/mo est. one-time purchase |
| 250,000 validation testsA still has no paid tier listed. | Free | $149/mo est. one-time purchase |
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.