What is Lero?
Lero is a blazing-fast, API-first email validation service built for modern teams and scrappy startups. Designed to verify any email address in under 50 milliseconds, Lero blends real-time speed, full-stack verification, and founder-friendly pricing to ensure your emails reach real humans—not dead inboxes.
Whether you're a SaaS startup capturing sign-ups, a marketer cleaning your outbound lists, or an enterprise managing millions of addresses, Lero fits seamlessly into your workflow. It's the silent powerhouse behind email hygiene, protecting your sender reputation and lifting your deliverability.
Why Lero Exists
Behind every great product is a story. Lero's founders built an AI assistant for vacation-rental hosts—until their email campaigns started bouncing at an alarming rate. The available validators were too slow, unreliable, or overpriced. So, they built Lero—originally for their own needs.
What started as a solution to one team's bounce nightmare is now helping thousands protect their domain reputation. Lero was created by people who truly understood the problem because they lived it.
What sets Lero apart?
- Built for developers and growth teams.
- A powerful email verification engine with sub-50 ms latency.
- Transparent, usage-based pricing—no lock-ins, no surprises.
Key Features at a Glance
Lero's secret lies in its precision and simplicity. Here's what it offers:
| Feature | Details |
|---|---|
| Sub-50 ms response time | Fast enough for live form checks and cold outreach automation. |
| 97.3% verified accuracy | Independently audited to ensure trustworthy results. |
| Full-stack email validation | MX check, SMTP ping, disposable and catch-all detection in one request. |
| Realtime & bulk capabilities | Validate single emails or clean entire lists via upload or API. |
| Pay-as-you-go pricing | Start at $0.0003/check. First 500 validations are completely free. |
| Slack-level support | Fast replies from the builders—no waiting in ticket queues. |
Deep Dive into Lero's Technology
Lero's verification engine runs a multi-stage validation pipeline, instantly assessing whether an email address is real, safe, and worth sending to.
Key components include:
- Syntax & DNS Validation: Checks format and domain-level health.
- SMTP Check: Pings the mail server without sending an email.
- Catch-all & Disposable Detection: Filters addresses that accept everything or auto-expire.
- Spam Trap Shielding: Proactively avoids common traps and honeypots.
The result? A clear verdict: valid, risky, or invalid—delivered in milliseconds, so your workflows never slow down.
API Overview: Fast, Clean, and Scalable
Lero is API-first—meaning developers love it from the first line of code.
Highlights:
- RESTful design with simple POST requests.
- JSON responses with detailed status info.
- Rate-limited by volume, not by tier.
- Latency under 50 ms even at scale.
Whether you're building a custom CRM, integrating into a signup flow, or powering email-based automation, Lero's developer docs and SDKs make integration seamless.
Use Cases for Lero
Lero isn't just for email marketers—it powers reliability across multiple verticals:
- SaaS Sign-ups: Prevent bad data from entering your user database.
- Cold Outreach Campaigns: Improve delivery and response rates.
- CRM Hygiene: Clean up stale contacts before you hit send.
- Lead Gen Forms: Block fake, mistyped, or burner emails at entry.
- Email Marketing Platforms: Validate lists before importing to ESPs.
Lero vs. Traditional Email Verifiers
| Feature | Lero | Legacy Verifiers |
|---|---|---|
| Speed | Under 50 ms | Often >1 second |
| Pricing | From $0.0003/check | From $0.001–$0.01/check |
| Accuracy | Independently audited 97.3% | Unverified claims |
| Support | Slack-level, direct from team | Email-only, long wait times |
| Startup Friendly | Yes | Typically built for enterprises |
Lero's approach is transparent, lightning-fast, and built for scale. You won't find hidden fees, vague accuracy claims, or clunky onboarding here.
Accuracy That Stands Out
Lero proudly claims 97.3% accuracy, but it's not just marketing fluff. That figure comes from independent audits and long-term testing across various domains and providers.
Why does accuracy matter?
- Fewer bounces = higher domain reputation.
- Better inbox placement = higher engagement.
- Cleaner data = more precise targeting and lower ad costs.
Enterprise-Grade Security & Compliance
Lero understands that email addresses are sensitive data.
Security & compliance highlights:
- Data encrypted in transit and at rest.
- GDPR-ready and hosted in the EU.
- SOC 2 compliance underway to meet enterprise IT standards.
Trust is baked into the infrastructure, not tacked on later.
How Lero Supports Founders
From pricing to support, everything about Lero is designed with founders and growth teams in mind.
- No monthly minimums.
- Pay only for what you use.
- Auto-volume discounts kick in as you scale.
- Need help? Talk directly to the builders on Slack or email.
Getting Started with Lero
You can get started with Lero in under five minutes—no credit card required.
Here's how:
- Sign up at https://www.leromail.com/auth/signin
- Get 500 free email validations
- Validate a list or test a few emails
- See bounce rates drop—and conversions rise
Real-world Results from Using Lero
Users who integrate Lero typically report:
- 25–40% reduction in bounce rates
- 10–30% improvement in inbox placement
- Savings of hundreds to thousands per month in email platform fees
Some founders even embed Lero's API directly in their signup forms to block junk before it gets into their CRM.
Common Questions About Lero
Q1: How does Lero validate emails so fast?
Lero's proprietary pipeline runs checks in parallel and uses persistent SMTP tunnels, reducing latency to sub-50 ms.
Q2: Is there a free plan?
Yes - your first 500 email validations are free, no strings attached.
Q3: Can I use Lero for bulk list cleaning?
Absolutely. Upload a CSV or hit the bulk API endpoint. You'll get the same high accuracy.
Q4: Is Lero GDPR-compliant?
Yes. Lero is hosted in the EU. SOC 2 compliance is underway.
Q5: Do I need to be technical to use Lero?
Not at all. While the API is developer-friendly, non-technical users can upload CSVs directly via the dashboard.
Q6: Does Lero detect disposable and catch-all emails?
Yes—both are part of the full-stack verification process.
Testimonials & Social Proof
"We cleaned 10K leads in under a minute, and saw a 35% drop in bounces. Game-changer."
— SaaS Founder
"Finally, a verifier built by people who *get* startups. Lero is ridiculously fast and affordable."
— Growth Hacker
"We added it to our sign-up form and instantly reduced fake signups by 40%."
— Product Manager
Integration & Developer Experience
Lero is built API-first and makes the developer experience delightful.
- Open API documentation
- Example requests in cURL, Python, Node.js
- Webhooks and Zapier/Make support coming soon
- SDKs and CLI tools in progress
Plans, Pricing & Value Proposition
Lero offers transparent, usage-based pricing that scales with your needs:
| Emails Validated | Price per Email | Total Cost |
|---|---|---|
| 1 - 500 | FREE | $0 |
| 501 - 10,000 | $0.0003 | $2.85 - $57 |
| 10,001 - 100,000 | $0.00025 | $57 - $570 |
| 100,001 - 1,000,000 | $0.0002 | $570 - $5,700 |
| 1,000,001+ | $0.00015 | $5,700+ |
- No monthly fees
- No contracts
- No surprises
Lero is committed to being the most transparent and cost-effective solution on the market.
Try Lero Today
Ready to protect your sender reputation, save on ESP costs, and clean your first list?
➡️ Sign up now to get 500 free validations.
Experience Lero's power - without touching your wallet.