Block fake signups
before they cost
you money.
Built for SaaS and AI products giving away valuable resources. Stop disposable signups before they consume your API credits, SMS costs, and server time.
No credit card required • 200 free requests/mo • Low-Latency Edge API
Static blocklists miss newly created disposable domains.
Modern trial abusers don't use 10minutemail. They buy $1 custom domains and set up catch-all routing. SignGuard's dynamic risk engine catches what static lists miss.
| Email Pattern / Abuse Type | Static CSV Blocklist | SignGuard Engine | Impact on Your SaaS |
|---|---|---|---|
| spammer@10minutemail.com Basic Disposable Email | Blocked | Blocked | Misses newly created disposable domains. |
| abuser@cheap-1dollar-domain.xyz Freshly Registered Custom Domain | MISSED | BLOCKED (Age: 1d) | Stops free-trial abusers using $1 domains to drain your API credits. |
| user+trial88@catchall-domain.com Wildcard / Catch-All Routing | MISSED | CHALLENGE (2FA) | Prevents infinite signups from a single catch-all mailbox. |
| founder@stripe.com High-Value Corporate Email | Allowed | ALLOWED (Score: 0.0) | Zero friction for legitimate paying customers. |
Integration takes 2 minutes.
Don't spend days building email validation. Just ping our endpoint.
curl -X POST https://api.signguard.co/v1/check \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"email": "user@hidepost.net"}'
# 2. Block Fraud
{
"decision": "block",
"score": 0.89,
"signals": {
"typosquatting": 0.6
},
"reasons": [
"high_risk_custom_domain"
],
"is_catch_all": true,
"domain_age_days": 3
}
Everything you need.
A complete suite of deliverability and fraud prevention tools.
Continuously Updated Intelligence
Stay protected without maintaining your own blocklist. We continuously update our threat intelligence to catch new disposable providers.
SMTP Mailbox Check
We communicate directly with the mail server to verify if the inbox actually exists, without sending an email.
Catch-All Detection
Identify domains that accept any email address prefix, which ruins deliverability and artificially inflates your user counts.
Typosquatting Engine
Catches gmaiil.com, yahooo.com, and lookalike domains that trick users into signing up with fake provider addresses.
Smart Risk Scoring
Combines domain age, catch-all status, MX records, role account detection, plus-alias patterns, and subdomain analysis into a single 0–1.0 risk score.
Built for the signup critical path.
Your abuse protection shouldn't become another signup dependency. SignGuard combines cloud threat intelligence with an SDK-level local fallback, so temporary API failures don't have to become signup failures.
Keep signups running
If the Cloud API times out, returns a 5xx, or is unreachable, the SDK instantly falls back to a bundled local engine. You still get disposable-domain, DNS/MX, and typosquatting checks when the Cloud API is unavailable.
Know what happened
Every result explicitly states whether it was evaluated by the Cloud or Local fallback, allowing you to audit decisions and monitor degraded states.
Avoid cascading latency
Repeated network timeouts trigger a circuit breaker that temporarily routes traffic straight to the local engine. This prevents API latency from compounding and slowing down your web workers.
Your agents can check email risk natively.
Point Claude, Cursor, or any MCP-compatible agent at SignGuard. It can screen signups, leads, or support tickets seamlessly — no glue code, no separate integrations.
- One config line. Add the SignGuard MCP server to any agent's tool list.
- No custom wrapper. Agents call the check tool directly — same data, same latency.
- Automated qualification. Let agents reject bad leads before a human ever sees them.
"email": "abuser@custom-domain.xyz",
"is_disposable": false,
"domain_age_days": 1,
"is_catch_all": true
}
Enterprise validation.
Solo-dev pricing.
Up to 10x cheaper than legacy enterprise validators. No hidden fees, cancel anytime.
Perfect for side projects and local testing.
- Up to 200 protected signups per month
- 74,781+ Domain Blocklist
- Low-Latency API
- Python, JS & cURL SDK
- 1 API Key
- Custom Allowlist / Blocklist
- SMTP Mailbox Verification
For growing SaaS apps stopping trial fraud.
- Up to 20,000 protected signups per month
- Dynamic Domain Age Check
- Typosquatting Engine
- MCP Server (Claude & Cursor)
- Custom Block/Allow Lists
- Batch API (up to 100/call)
Maximum deliverability & deep verification.
- Up to 100,000 protected signups per month
- Everything in Starter, plus:
- SMTP Mailbox Existence Check
- Wildcard Catch-All Detection
- Email Finder (name → verified)
- Priority Email & Slack Support
- 99.9% Target Uptime
Your next fake signup costs you real money in wasted API credits.
Join developers who stopped bleeding money on trial abusers. Setup takes less than 2 minutes. First 200 checks are free, forever.