We Give Away 5,000 API Calls. Here's Why.

Try searching for “free email validation API” and you will find a graveyard of landing pages promising free tiers that barely let you test. ZeroBounce gives you 100 one-time checks. Kickbox gives you 100. NeverBounce has no free tier at all — you need a credit card to send your first request. TrueList offers 200 per month.

We think that is backwards. You cannot evaluate an email validation tool with 100 checks any more than you can evaluate a database with 100 rows. You need enough volume to test with a real list, see real results, and make a real decision. That is why every MailSentry account starts with 1,000 free checks per month plus 5,000 bonus credits.

The Problem With Paywalled APIs

Here is what a Hacker News commenter said about the state of email validation tools:

“I noticed a lot of the email validation services out there: Do not have an API / Are behind a paywall to try the API / Are priced way too high / Have inconsistent or non-intuitive APIs.”

This is not an edge case complaint. It captures the experience of every developer who has tried to integrate email validation into a signup form, a CRM workflow, or a data pipeline. The evaluation process looks like this:

1. Find a provider. Sign up. Discover the free tier gives you 100 checks.
2. Burn through those 100 checks in minutes testing your integration code — not even validating real emails yet.
3. Hit the paywall. Now you need to decide: pay for a plan you have not properly evaluated, or move on to the next provider and repeat the cycle.

The result is that developers either pick the cheapest option without testing quality, or chain multiple providers in a “waterfall” because they do not trust any single one. Both outcomes are bad for the developer and bad for the provider.

Why 5,000 Credits Changes the Equation

With 5,000 bonus credits, here is what you can actually do:

• Validate a real list. Export 5,000 contacts from your CRM, run them through the API, and see the actual results — valid, invalid, risky, catch-all — for your data, not a sandbox demo.
• Test your integration end-to-end. Build the signup form validation, the webhook handler, the batch processing script. Test with real traffic, not mock data.
• Compare results. If you are evaluating multiple providers, run the same list through each one. 5,000 checks gives you a statistically meaningful sample to compare accuracy, speed, and response quality.

The 5,000 bonus credits are consumable — they are used after your 1,000 monthly plan allocation is exhausted. They never expire. So if you only use 200 checks per month, those bonus credits sit there until you need them.

What You Get on the Free Tier

Some providers strip features from their free tier — no SMTP verification, no risk scoring, no typo correction unless you upgrade. We do not do that. Every MailSentry account, free or paid, gets:

• All 11 validation layers (syntax, MX, disposable, role-based, free provider, typo, SMTP, gibberish, spam trap, domain age, abuse)
• Quality score (0–100) with every response
• Typo correction (gmial.com → gmail.com)
• Catch-all detection with confidence scoring
• Extended verification depth (SMTP re-probe for greylisting resolution)
• Full API access — same endpoints, same response format, same rate limits tier

The only difference between free and paid is volume. Not features. Not accuracy. Not API access.

How Bonus Credits Work

The credit system is simple:

1. Monthly allocation resets. Free plan: 1,000 checks/month. Starter: 10,000. Pro: 50,000. Resets on the 1st of each month.
2. Bonus credits are consumed after the monthly limit. If you use 1,200 checks in a month on the free plan, 1,000 come from your plan allocation and 200 are deducted from your bonus balance.
3. Bonus credits never expire. Use them this month, next month, or six months from now.
4. Purchased credits stack. If you buy a 5,000 credit pack from the dashboard, those are added to your bonus balance alongside any remaining signup credits.
5. Hard cap at zero. When both your monthly allocation and bonus credits are exhausted, the API returns a 402. No surprise charges. No automatic upgrades.

The Business Logic

Giving away 5,000 API calls is not charity — it is a conversion strategy. The math is straightforward:

A developer who validates 5,000 real emails and sees that 12% are invalid, 3% are disposable, and 2% have typos is a developer who understands the value of email validation. They have seen the data. They know what happens when those bad addresses hit their database. They do not need a sales call or a case study — they have their own evidence.

A developer who gets 100 free checks, burns them on test data, and hits a paywall has no evidence. They have a landing page promise and a pricing page. That is not enough to justify adding a dependency to a production system.

We would rather have 1,000 developers who have properly tested the product and 200 of them convert, than 5,000 developers who bounced off a paywall and zero of them convert.

Try It

Sign up at mailsentry.dev/signup. No credit card. No approval queue. Your API key is issued instantly, and your 5,000 bonus credits are already in your account.

Validate a real list. Look at the scores. Check the typo corrections. See how many disposable addresses are hiding in your database. Then decide if it is worth $9/month for 10,000 checks.

That is the pitch. The product is the proof.