Seven checks. One verdict.

Why pre-send validation is the single highest-leverage email investment

Pre-send validation — running every address through the 7-check engine immediately before /api/v1/mail/send executes — is the single most cost-effective intervention available to most email programs. The economics are stark: a validation check costs a fraction of a cent; a bounce costs you the send credit plus the reputation damage that follows.

The bounce-to-spam-folder pipeline

Mailbox providers monitor sender bounce rate as a primary reputation signal. Bounce rates above 2 percent trigger reputation degradation at Gmail and Microsoft. Bounce rates above 5 percent trigger temporary blocks. Pre-send validation drops typical bounce rates from 5-10 percent on cold lists to under 0.5 percent — a dramatic reputation-protection lever. The downstream effect is even more valuable: lower bounce rate means higher inbox-placement percentage, which means more revenue per send for marketing campaigns and higher conversion on transactional flows.

Spam-trap protection is reputation protection

Spam-trap hits are the single most damaging event in an email-program lifecycle. A single recycled-trap hit on a major mailbox provider can drop your domain reputation tier overnight. Pristine-trap hits — addresses created from scratch and seeded specifically to catch list scrapers — typically result in same-day blocklisting on Spamhaus or Barracuda. Recovery from a Spamhaus listing takes 30-90 days of remediation. Pre-send validation cross-references every address against known-trap databases and the WHOIS domain-age signal, catching these addresses before they ever reach your send queue.

Disposable-domain detection prevents fraud loops

Many free-trial abuse and fraud-signup workflows use disposable email services (10minutemail, mailinator, throwaway domain registrations). The WHOIS domain-age check is uniquely powerful here — a domain registered within the last 24 hours that has never appeared in any other system is overwhelmingly likely to be a disposable. Catching these at signup time, before you provision the trial or send the welcome email, eliminates an entire class of fraud loss.

Integration patterns

Signup form validation: hit the real-time API in your signup handler before account creation. Return a friendly error for failed addresses (“Please double-check your email — we could not verify this address”). Best practice is to distinguish between hard failures (typos, malformed) and soft failures (catch-all, role-account) and only block the hard ones.

List-import validation: when importing a contact list, queue it through the bulk validation processor first. Quarantine high-risk and invalid addresses to a separate list and only import the verified-deliverable ones. The bulk processor returns a per-address risk score so you can apply your own thresholds.

Pre-send hook: enable validation on every send by toggling the pre-send hook in your dashboard's Email Validation settings. Every address passes through the validator immediately before /api/v1/mail/send executes. Failed addresses are auto-suppressed and the original send returns a structured error indicating which addresses were rejected. Minimal latency overhead (under 300ms p95) and dramatic reputation protection.

Frequency and cache strategy

Verdicts cache for 7-30 days depending on the verdict type — definitive verdicts (clear invalid, clear spam-trap, clear catch-all) cache longer; ambiguous verdicts (risk-flagged, soft-deliverable) cache shorter. The recommended re-validation cadence is monthly for active marketing lists and 90-day intervals for transactional address pools. Bulk re-validation is cheap thanks to caching — re-running last month's 100k-address list typically pays for only the newly-added addresses plus a small percentage of expired verdicts.