verified Built for SaaS Signup Quality

Email verification built for SaaS teams who care about signup quality

Stop fake accounts before they inflate your MAU. Catch disposable, role-based, and catch-all addresses at the signup form, not after your activation drip has already bounced. Mailsfinder's real-time verification API plugs into any SaaS stack in an afternoon and runs on a 300,000 credit pool from $9.99 per month.

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check_circle50 free credits, no card check_circleSub-second API response check_circleUnder 1% bounce rate

shield_person

Signup Quality Dashboard

Last 30 days, sample SaaS

Signups received 48,210

Disposable blocked 2,840 (5.9%)

Role-based flagged 1,120 (2.3%)

Catch-all soft-flagged 3,460 (7.2%)

Activation bounce rate 0.7%

Real-time, in-flow

Trusted by product-led SaaS, lifecycle teams, and growth engineers in 40+ countries

FlowOps LumenAI Northwind PulseDB GreenBox StackRoute

Why SaaS teams pick Mailsfinder

Three things every product-led team asks about first

A real-time API the form can call, granular detection your backend can branch on, and webhooks for everything that does not need to block.

bolt

Real-time form API

Drop a single fetch call into your signup form's submit handler. Mailsfinder returns a verification verdict in 200ms to 800ms so the user never feels the round trip. Block hard fails, allow soft passes, log everything to your warehouse.

policy

Disposable and role-based detection

Explicit flags for 5,000+ disposable domains, role accounts (info@, admin@, support@), free providers, and catch-all servers. Branch on each category in your signup policy, so legitimate small-team buyers using shared inboxes are not blocked alongside Mailinator throwaways.

webhook

Webhooks for async backend

Queue a verification job from your backend with a webhook_url and get the verdict POSTed back when it is ready. Perfect for activation drip pre-flight checks, list re-engagement scrubs, and any workflow where the form does not need to wait.

How it works

From signup form to clean warehouse table in four steps

The same flow whether you ship a self-serve trial or a freemium product with a 30,000 signup per month firehose.

Drop the API call

Add a single fetch to /v1/verify in your signup form submit handler or backend route. About 15 minutes of work for a frontend engineer, including error handling.

Capture intent at signup

Mailsfinder runs SMTP, MX, syntax, disposable, role, and catch-all checks. The verdict comes back with a status plus structured flags your code can branch on cleanly.

Block invalid in flow

Reject hard fails with an inline error, allow soft passes through, and route catch-all results into a watchlist. Your activation drip only ever sees addresses likely to deliver.

Log to your warehouse

Pipe every verification verdict into Snowflake, BigQuery, or Postgres. Now your growth team can slice activation funnels by verification status and stop debugging bad data.

Deep dive

A single API call, every verdict your signup policy needs

No SDK to install, no complicated auth flow. POST an email to /v1/verify with your API key and Mailsfinder returns a structured JSON verdict your code can branch on directly. Most SaaS teams ship the integration in under an hour.

check_circle Status field with valid, invalid, catch_all, unknown so your code can branch cleanly.
check_circle Granular flags for disposable, role, free, mx_found, smtp_check so policy decisions are explicit.
check_circle Score (0-100) so you can tune your block threshold by user cohort.
check_circle Webhook fallback for stubborn domains, so your form never blocks on a slow SMTP host.

verify_signup.sh

curl -X POST https://api.mailsfinder.com/v1/verify \
  -H "Authorization: Bearer $MF_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "sarah@acme.io",
    "webhook_url": "https://your-app.com/hooks/mf"
  }'

data_object 200 OK, response

{
  "email": "sarah@acme.io",
  "status": "valid",
  "score": 96,
  "disposable": false,
  "role": false,
  "free": false,
  "mx_found": true,
  "smtp_check": true,
  "catch_all": false,
  "did_you_mean": null
}

Pricing

Pricing that fits SaaS signup volume, not a per-verification toll

300,000 credits per cycle covers 30K to 100K signups per month for most teams. Add Lifetime when you want a credit pool that never expires.

Monthly

For SaaS handling 30K to 100K signups per month.

$9.99 /month

check300,000 verification credits per cycle
checkReal-time Verifier API plus webhooks
checkDisposable, role, catch-all flags
check600 req/min rate limit
checkFinder and Enrichment APIs included
checkPriority email support

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Annual

Lock in 20% savings on a year of verification credits.

$7.99 /month

Billed $95.88 per year

check300,000 verification credits per cycle
checkReal-time Verifier API plus webhooks
checkDisposable, role, catch-all flags
check600 req/min rate limit
checkFinder and Enrichment APIs included
checkPriority email support

Choose Annual

Lifetime

One-time payment, two million credits, no recurring bill.

$249 one-time

check2,000,000 verification credits (lifetime pool)
checkFinder and Verifier APIs
check5,000 exports per month
check1,000 Enrichment calls per month
check25 Signals per month
check300 req/min, lifetime access

Get Lifetime

Top-up credit packs for signup spikes

Stack on any plan. Credits never expire. Useful for Product Hunt launches, paid campaign bursts, or quarterly list re-engagement scrubs.

10K

credits

22K

credits

42K

credits

$14.99

100K

credits

$29

250K

credits

$59

SaaS use cases

Built for the four signup-quality motions every SaaS runs

Product-led signup, activation drip hygiene, free-tier abuse prevention, and win-back list scrub. One verification pool, four playbooks.

rocket_launch

Product-led SaaS signup

Block disposable addresses at the signup form so fake accounts never enter your trial pool. Keep MAU honest, keep conversion analytics clean, and stop the free-tier abuse loop before it starts.

forward_to_inbox

B2B activation drip pre-flight

Verify every new email before it enters Customer.io, Klaviyo, or HubSpot. Activation drips stay under 1% bounce, inbox placement holds on Gmail and Outlook, and your lifecycle team stops chasing deliverability ghosts.

security

Free-tier abuse prevention

Same user, ten Mailinator addresses, ten free trials. Mailsfinder's disposable detection blocks the pattern at the form, so finance stops paying for fake usage and product stops shipping features tuned to fraudulent cohorts.

cleaning_services

Win-back list hygiene

Before sending a re-engagement campaign to 6-month dormant users, scrub the list through the webhook API. Drop hard fails, flag catch-all, and protect sender reputation on the one campaign that actually needs to land in the inbox.

FAQ

Questions SaaS teams ask before integrating

How fast is the verification API for signup forms? expand_more

Mailsfinder returns a verification verdict in 200ms to 800ms on most requests, which keeps signup flows feeling instant. For SaaS signup forms, you can call the API on form submit and resolve before the user lands on the next screen. If a deeper SMTP probe is needed for a stubborn domain, we recommend falling back to a webhook so the form never blocks on a slow third-party mailbox.

What is the false-positive rate on catch-all domains? expand_more

Catch-all domains accept every address at the SMTP layer, so no verifier can prove deliverability with 100% confidence. Mailsfinder returns a separate catch_all status (not valid, not invalid) so your SaaS can decide policy. Many teams allow catch-all signups but flag them for soft-bounce monitoring in the first 7 days. Across non-catch-all domains, false positives stay under 1%.

Is Mailsfinder GDPR compliant for EU user verification? expand_more

Yes. Mailsfinder operates as a data processor under GDPR Article 28 and processes verification requests in EU data centers when configured. Verification is a legitimate interest under recital 47 for fraud prevention and deliverability, but you should still disclose verification in your signup privacy notice. A DPA is available on request.

How do I set up webhooks for async backend verification? expand_more

Submit a verification job to POST /v1/verify with a webhook_url field, and Mailsfinder will POST the result to your endpoint when verification completes. This is the recommended pattern for lifecycle drip pre-flight checks, list re-engagement scrubs, and any workflow where you do not need the answer in the request-response cycle. Signed webhook payloads use HMAC-SHA256.

What are the API rate limits on each plan? expand_more

Monthly and Annual plans get 600 requests per minute on the Verifier API. The Lifetime plan caps at 300 req/min. For a SaaS handling 30,000 to 100,000 signups per month, 600 req/min covers peak signup bursts during launches, Product Hunt days, and paid campaign spikes.

Does Mailsfinder integrate with Klaviyo, HubSpot, or Customer.io? expand_more

Mailsfinder's REST API plugs into n8n, Make, and Zapier (via their HTTP/webhook actions), which cover Klaviyo, HubSpot, Customer.io, Iterable, and most lifecycle ESPs. The typical pattern: a new user lands in your data warehouse, a workflow triggers a POST to the Mailsfinder verify endpoint, and clean addresses sync to the ESP while invalid ones get tagged for suppression.

Can I block disposable and role-based emails at signup? expand_more

Yes. The verification response includes explicit flags for disposable (Mailinator, TempMail, Guerrilla Mail, plus 5,000+ tracked domains) and role-based (info@, admin@, support@) addresses. Most SaaS teams block disposable hard at signup and surface a soft warning for role-based, since legitimate buyers sometimes use shared inboxes.

How does verification protect activation drip deliverability? expand_more

Activation drips often see 5% to 12% bounce rates when signup forms are unverified, which signals spam-trap risk to inbox providers and tanks placement for legitimate users. Running every new email through Mailsfinder before adding to the lifecycle ESP typically brings bounce rate under 1% and lifts inbox placement on Gmail and Outlook by measurable margins within a few weeks.

Ship verified signups by the end of the week

Start with 50 free credits. No card needed. Drop the API into your signup form in an afternoon, watch fake accounts and bounce rate fall before your next sprint review.

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