How Does Email Validation Work?
Understanding the hybrid validation layer that protects your sender reputation before a single email is sent
Quick Answer
Superkabe validates every incoming email before it reaches your sending platform. Invalid emails are blocked automatically. The system uses a hybrid approach: fast internal checks first, then external API verification for borderline cases — saving you money while catching bad addresses before they bounce.
How the Hybrid Validation Layer Works
Superkabe doesn't rely on a single validation method. Instead, it runs a two-stage pipeline that balances speed, accuracy, and cost.
Stage 1: Internal Checks (Free)
Every email passes through these checks instantly, at zero cost. Most obviously invalid emails are caught here.
- • Syntax validation — Catches typos like missing @ or double dots
- • MX record lookup — Confirms the domain can actually receive email
- • Disposable domain detection — Blocks throwaway addresses (mailinator, guerrillamail, etc.)
- • Catch-all detection — Flags domains that accept any address (risky for bounce rates)
Available on all plans. No API credits consumed.
Stage 2: MillionVerifier API (Paid)
Emails that pass internal checks but are flagged as risky get sent to MillionVerifier for deep verification.
- • SMTP handshake — Connects to the mail server to verify the mailbox exists
- • Inbox activity signals — Checks for signs of an active, real mailbox
- • Role-based detection — Identifies addresses like info@, support@, admin@
- • Spam trap detection — Catches known spam trap addresses
Only called when needed. DomainInsight caching reduces API calls further.
Validation Statuses Explained
The email address is confirmed to exist and is safe to send to. No bounce risk.
The email might be deliverable but has risk factors (catch-all domain, role-based address, low activity). May be sent depending on your plan tier.
The email address does not exist, the domain has no mail server, or it failed SMTP verification. Blocked automatically — never sent.
Verification was inconclusive (server timeout, greylisting). Treated as risky and may be retried later.
Why Is My Lead Showing as “Invalid”?
When a lead shows the Invalid status, it means Superkabe determined the email address cannot receive mail. Common reasons include:
- • The mailbox doesn’t exist on the recipient’s server (e.g., the person left the company)
- • The domain has no MX records — it simply cannot receive email
- • The address uses a known disposable email provider
- • Syntax errors in the address (missing @, invalid characters)
What happens: Invalid leads are permanently blocked and will never be sent to your sending platform. This protects your bounce rate and sender reputation.
DomainInsight Caching: Saving API Costs
Superkabe caches domain-level validation intelligence using DomainInsight. When the system validates an email, it stores what it learned about the domain — MX records, catch-all status, disposable classification, and blacklist status.
How It Saves Money
• First email from a domain: Full validation runs (internal + API if needed). Domain data is cached.
• Subsequent emails from the same domain: Internal checks reuse cached domain data. Many validations skip the API entirely.
• Example: If you import 500 leads from 50 companies, only ~50 domain lookups are needed instead of 500.
DomainInsight cache refreshes periodically to stay accurate. Stale data is automatically invalidated.
Validation by Plan Tier
Internal Checks Only
All four internal checks run on every lead (syntax, MX, disposable, catch-all). No external API calls. Great for small volumes where most leads come from reliable sources like LinkedIn.
Internal + API for Risky Leads
Internal checks run first. Leads flagged as risky (catch-all domains, role-based addresses) are sent to MillionVerifier for deep verification. Valid and invalid leads skip the API. This is the sweet spot for most teams.
Maximum API Coverage
All leads that aren’t obviously invalid get API verification. Even “valid” internal results are double-checked externally. Best for high-volume senders where every bounce matters and the cost of a bounce exceeds the cost of verification.
Example: What Happens When a Lead Is Ingested
1. Lead arrives via Clay webhook: john@acmecorp.com
2. Syntax check: Pass (valid format)
3. MX lookup: Pass (acmecorp.com has MX records — cached from DomainInsight)
4. Disposable check: Pass (not a disposable domain)
5. Catch-all check: Flag — acmecorp.com is a catch-all domain (risky)
6. Result so far: Risky. On Growth/Scale tiers, the lead is sent to MillionVerifier.
7. API result: Valid — SMTP handshake confirmed the mailbox exists.
8. Final status: Valid. Lead proceeds to health gate and routing.