Unlimited Email Verification:
Flat Rate API, Zero Overage Fees
Unlimited email verification with dedicated concurrent threads and flat monthly pricing from $250/mo. No per-email costs, no caps, no surprises. Scale from thousands to millions of verifications without worrying about overages. Cancel anytime.
What Is the Unlimited Email Verification API?
The Unlimited Email Verification API replaces traditional credit-based pricing with a thread-based subscription model. Instead of paying per email verified, you pay a flat monthly fee for dedicated concurrent threads that process verifications in parallel, with no cap on monthly volume.
Each thread represents a dedicated connection to our verification infrastructure. Think of threads as workers: one thread verifies one email at a time, but since each verification completes in milliseconds, a single thread can process tens of thousands of emails per day. Add more threads to proportionally increase throughput.
- Thread-Based, Not Credit-BasedPay for concurrent capacity, not per email. Verify as many emails as your threads can handle.
- Flat Monthly PricingPredictable costs each month. No surprise bills, no overages, no per-email fees.
- Same 99.7% AccuracyIdentical 17+ factor SMTP verification engine used across all our products.
- Scale Up or Down AnytimeAdd or remove threads from your dashboard. No long-term contracts required.
| Feature | Credit-Based | Unlimited API |
|---|---|---|
| Pricing model | Per email | Flat monthly |
| Monthly volume | Limited by credits | Unlimited |
| Overage fees | Yes, if credits run out | Zero - never |
| Cost at 1M emails | $409+ | $250 (1 thread) |
| Predictable billing | Varies by volume | Fixed each month |
| Best for | Occasional use | Continuous high-volume |
How Thread-Based Pricing Works
A simple, scalable model designed for high-volume email verification. No credits, no limits, no overage fees.
1 Thread = 1 Concurrent Verification
Each thread is a dedicated connection that processes one email verification at a time. Since each check completes in milliseconds, one thread handles tens of thousands of emails per day.
More Threads = Faster Parallel Processing
Add threads to proportionally increase throughput. 10 threads process 10 emails simultaneously, delivering 10x the speed of a single thread for large-scale verification.
Flat Monthly Rate, Zero Overages
You pay a fixed monthly fee per thread. No per-email charges, no caps, no surprise bills. Your cost stays the same whether you verify 100,000 or 10 million emails.
Scale Up or Down Anytime
Increase threads during busy periods and reduce them when volume drops. No long-term contracts. Upgrade, downgrade, or cancel directly from your dashboard at any time.
Unlimited Email Verification API Pricing
Choose your thread count based on throughput needs. All plans include unlimited verifications and zero overage fees.
Key Features of the Unlimited Email Verification API
Everything you need for high-volume, continuous email verification at a predictable cost.
Truly Unlimited Verifications
No monthly caps, no credit balances, no volume limits. Verify as many emails as your threads can process each month. Your cost stays the same whether you verify 50,000 or 50 million.
Dedicated Concurrent Threads
Each thread is a dedicated connection to our private cloud verification infrastructure. Threads run in parallel for maximum throughput, with consistent sub-second response times even under heavy load.
Flat Monthly Pricing
Know exactly what you pay each month. No per-email fees, no usage tiers, no surprise overages. Budget with complete confidence using our fixed-rate thread model.
Zero Overage Fees
Unlike credit-based services where you pay more when credits run out, our unlimited model has zero overage fees. Your flat rate covers all verifications, period.
Same 99.7% Accuracy
The Unlimited API uses the identical 17+ factor SMTP verification engine as our Real-Time API and Bulk Verifier, delivering 99.7% accuracy on every check.
Month-to-Month, Cancel Anytime
No annual contracts, no lock-in periods. All plans bill month-to-month. Upgrade, downgrade, or cancel your threads anytime directly from your dashboard.
API Response Example
Every verification returns a detailed JSON or XML response with the status, event, intelligence flags, and free MX enrichment data.
"status": "passed",
"event": "mailbox_exists",
"details": "The address provided passed all tests.",
"email": "example@gmail.com",
"emailSuggested": "",
"mailbox": "example",
"domain": "gmail.com",
"isComplainer": false,
"isDisposable": false,
"isFreeService": true,
"isGibberish": false,
"isOffensive": false,
"isRoleAccount": false,
"timestampUTC": "2026-01-22T04:52:08Z",
"execution": "0.03",
"mxEnrichment": {
"mxIp": "142.250.102.27",
"mxHostname": "alt4.gmail-smtp-in.l.google.com",
"mxCity": "",
"mxPostalCode": "",
"mxState": "Texas",
"mxStateISOCode": "TX",
"mxCountry": "United States",
"mxCountryISOCode": "US",
"mxContinent": "North America",
"mxContinentISOCode": "NA",
"mxTimezone": "America/Chicago",
"mxLatitude": "32.7797",
"mxLongitude": "-96.8022",
"mxIsp": "Google Servers",
"mxIspOrganization": "Google Servers",
"mxAsn": 15169,
"mxAsnOrganization": "GOOGLE"
}
}
Who Uses the Unlimited Email Verification API
From high-traffic forms to enterprise data warehouses, unlimited verification powers every high-volume use case.
High-Traffic Signup Forms
Validate every email at registration in real-time. Block disposable addresses, typos, and fake accounts before they enter your database. Dedicated threads ensure consistent speed during traffic spikes.
SaaS Platforms with Built-In Verification
Embed email verification directly into your SaaS product. Let your customers verify emails through your interface while the Unlimited API handles the backend processing at scale.
Data Warehouse Batch Processing
Process millions of historical email records from internal databases and data warehouses. Multiple threads churn through massive datasets with zero per-email fees eating into your budget.
CRM Continuous List Hygiene
Schedule automated verification jobs to keep your CRM clean. Run nightly or weekly sweeps across your entire contact database without worrying about credit consumption.
ESPs and Marketing Automation
Email service providers and marketing platforms integrate the Unlimited API to offer built-in verification to their customers. Validate emails at import, before sends, and during list maintenance.
Enterprise Lead Ingestion
Verify every lead as it enters your pipeline from web forms, third-party sources, and partner feeds. Ensure only valid, deliverable addresses reach your sales team and marketing campaigns.
Why Choose Unlimited Over Pay-Per-Email?
The more you verify, the more you save. Here's how unlimited stacks up against traditional credit-based pricing.
- Costs increase with every email you verify
- Fluctuates when volume spikes
- Budget is unpredictable month to month
- Teams hesitate to verify "just in case" emails
- Re-verifying aged lists eats into credits
- One flat monthly fee, no matter how many emails
- Volume spikes cost nothing extra
- Same predictable bill every month
- Verify every email without worrying about cost
- Re-verify your entire database monthly for free
When to Choose Unlimited vs Pay-As-You-Go
Both models use the same 99.7% accurate verification engine. The right choice depends on your volume and usage pattern.
| Criteria | Unlimited API | Pay-As-You-Go |
|---|---|---|
| Best for | Continuous high-volume verification | Occasional list cleaning |
| Pricing model | Flat monthly per thread | Per email verified |
| Monthly volume | Unlimited - no caps | Limited by credit balance |
| Overage fees | None - ever | Buy more credits when depleted |
| Real-time form validation | Ideal - dedicated thread capacity | Suitable for low traffic |
| Batch processing | Ideal - parallel threads | Suitable for small batches |
| Cost predictability | Fixed monthly bill | Varies with volume |
| Ideal volume | 100,000+ emails/month | Under 100,000 emails/month |
| Contract | Month-to-month | No contract - credits never expire |
Trusted by High-Volume Senders Worldwide
Enterprise teams and agencies rely on our unlimited API for mission-critical email verification.
"We switched from ZeroBounce to the unlimited API and our verification costs dropped from $8,000/mo to $2,300/mo. Same accuracy, 94% less spend."
"The thread-based model is genius. We run 20 threads 24/7 and verify our entire 15M contact database every month for a fraction of what we used to pay."
"We use some threads for real-time form validation and others for nightly list cleaning. The flexibility of the unlimited API is unmatched by any competitor."
Enterprise-Grade Security & Compliance
Your data is protected by military-grade encryption and industry-leading compliance certifications.
Zero-Knowledge Architecture
Even our own staff cannot access your data. Each client's verifications are processed in isolated encrypted containers.
Dedicated Thread Isolation
Your unlimited threads are fully isolated from other clients. No shared resources, no cross-contamination, no data leakage.
99.99% Uptime SLA
Redundant infrastructure with automatic failover. Service credits issued if we fail to meet our uptime guarantee.
Unlimited Email Verification API FAQ
Everything you need to know about unlimited email verification, thread-based pricing, and how it compares to pay-as-you-go.
What is an unlimited email verification API?
An unlimited email verification API is a subscription service that lets you verify an uncapped number of emails each month. Instead of paying per email, you pay a flat monthly fee based on how many concurrent threads (dedicated connections) you need. Each thread processes verifications in parallel with no volume limits.
How does thread-based pricing work?
Each thread is a dedicated concurrent connection to our SMTP verification infrastructure. One thread verifies one email at a time. Since each check completes in milliseconds, a single thread handles tens of thousands of emails per day. You pay a flat monthly rate per thread with zero overage fees, regardless of total volume.
How many emails can one thread verify per day?
Throughput depends on destination mail server response times. Major providers like Gmail and Outlook respond in milliseconds, while smaller servers may take longer. On average, each thread typically verifies tens of thousands of emails per day. We allow up to 60 seconds per verification before timing out.
Is this the same accuracy as pay-as-you-go verification?
Yes. The Unlimited API uses the identical 17+ factor verification engine, including SMTP mailbox verification, catch-all detection, disposable email filtering, spam trap identification, and role account detection. Both products deliver the same 99.7% accuracy.
What is the difference between unlimited and credit-based email verification?
Credit-based plans charge per email verified, so costs grow linearly with volume. The unlimited email verification API uses a flat monthly fee based on concurrent threads. If you verify more than 100,000 emails monthly, the unlimited model is typically the better value since your cost stays fixed no matter how many emails you verify.
Can I use the unlimited API for real-time form validation?
Absolutely. Dedicated threads provide consistent sub-second response times, making the Unlimited API ideal for real-time validation at signup forms, checkout pages, and lead capture forms, even during high-traffic periods.
Are there any rate limits or hidden caps?
No artificial rate limits and no hidden caps. Your thread count determines throughput. With 10 threads, you process 10 concurrent verifications simultaneously. Scale to 50+ threads for enterprise-speed verification. The only throughput factor is destination server response times.
Can I cancel or change my plan at any time?
Yes. All plans are month-to-month with no long-term contracts. You can upgrade, downgrade, or cancel your thread count at any time directly from your dashboard. Changes take effect on your next billing cycle.
How much does unlimited email verification cost?
Pricing starts at $250/month for 1 thread. Popular tiers include 5 threads at $1,200/mo, 10 threads at $2,300/mo, 20 threads at $4,600/mo, and 50 threads at $11,250/mo. All plans include unlimited verifications with zero overage fees. View all pricing tiers.
Is the unlimited API cheaper than paying per email?
For high-volume users, yes. With pay-as-you-go, your costs increase with every email you verify. With the unlimited model, you pay one flat monthly fee and verify as many emails as your threads can handle. The more you verify, the greater the value. Most customers who verify over 100,000 emails per month see significant savings compared to credit-based pricing.
How do I integrate the unlimited email verification API?
Use our simple REST API endpoint and receive JSON or XML responses. We provide comprehensive documentation and code examples in PHP, Python, Node.js, Ruby, Java, and more. Most integrations are completed in under an hour.
What payment methods do you accept?
We accept all major credit cards (Visa, Mastercard, Discover, American Express) through Stripe. Enterprise clients verifying at scale can request invoice billing for their deployment.
Is it really unlimited email verification?
Yes, truly unlimited. There are no hidden volume caps, no overage fees, and no throttling based on how many emails you verify. Your thread count determines how many verifications you can run concurrently, but the total number of verifications per month is uncapped. Whether you verify 100,000 or 10 million emails in a month, your cost stays the same. We can offer this because our thread-based pricing model aligns infrastructure costs with actual resource usage.
What is the fair use policy for unlimited verification?
There is no restrictive fair use policy. Unlimited means unlimited. The only constraint is your thread count, which determines concurrent processing capacity. Each thread can run 24/7 with no daily, weekly, or monthly limits on total verifications. If you need more throughput, simply add more threads. Enterprise clients routinely verify tens of millions of emails per month on our platform.
Can I use the unlimited API for both bulk lists and real-time validation?
Yes. The unlimited API uses the same REST endpoint as our standard real-time API, so it works for both single real-time verifications (signup forms, checkout pages) and programmatic batch processing of large lists. Many customers use it for both simultaneously, with some threads dedicated to real-time form validation and others processing background list cleaning jobs.
How does the unlimited email verification API compare to ZeroBounce or NeverBounce?
ZeroBounce and NeverBounce charge per email verified, which becomes extremely expensive at high volumes. For example, verifying 1 million emails monthly costs $2,000-4,000+ with per-email pricing. With our unlimited API at 10 threads ($2,300/mo), you can verify millions of emails for a fixed cost, potentially saving 80-95% compared to per-email competitors. All three services offer SMTP verification, but only Bulk Email Checker provides a true unlimited model with no volume caps.
Do I need a dedicated server or special infrastructure to use the unlimited API?
No. The unlimited API is a standard REST endpoint that works from any server, application, or device that can make HTTPS requests. There is no special software to install, no dedicated servers to provision, and no complex setup required. You simply send HTTP requests with your API key. The dedicated threads run on our infrastructure, not yours. Most integrations are completed in under an hour.
What SLA and uptime guarantee do you offer?
We guarantee 99.99% API uptime backed by a formal Service Level Agreement. Our verification infrastructure runs across multiple redundant data centers with automatic failover. If we fail to meet the uptime guarantee in any billing period, affected customers receive service credits. Enterprise clients can request custom SLA terms. Real-time status monitoring is available on our status page.
Start Verifying Unlimited Emails Today
Lock in predictable monthly costs with dedicated threads and zero overage fees. Scale your email verification without per-email charges.