Work-Email Waterfall

The confidence ladder is the product

| tier | cost | earns | |---|---|---| | infer | free, instant | `guess` / `likely` — corporate patterns from name + domain, ranked by real-world prevalence, MX-gated | | vendor | 1 credit, opt-in | `likely` / `confirmed` — a purpose-built B2B finder API; `confirmed` only above a deliverability score |

Inference can never return `confirmed`. Nothing has verified the local part, however cleanly the name parsed and however real the domain is — and that word is exactly what makes someone send without checking.

An unconfigured paid tier is SKIPPED SILENTLY, not attempted. Calling a vendor with an absent key burns a request to learn what the missing key already said.

Unknown is not "no"

The MX check keeps three states distinct: `true` (accepts mail), `false` (checked, no records, so every guess is dead on arrival) and `null` (could not check — DNS timeout, blocked egress, serverless network policy). Collapsing null into false is how a perfectly good company gets reported as unable to receive mail and every real address behind it is thrown away.

Scope, stated plainly

Business contact at a company you already have a relationship question about. It does NOT send anything — there is no mail path in the package. It does not enrich in bulk: one person, one call. It does not return personal addresses — the work-typed entry is preferred and a personal-only payload returns nothing rather than falling back to somebody's private inbox. And it does not guess phone numbers, because a name and a domain cannot imply one, so a miss there is a genuine miss.

Contact data decays roughly 22–40% a year. Keep the `checked_at`; nothing here is worth storing forever.

Verified

32 tests, 10 deliberate defects, 9 caught and 1 proved equivalent with its proof. Caught defects include an inferred guess labelled `confirmed`, a failed DNS lookup reported as "no MX", the unconfigured vendor tier calling out anyway, a personal address returned where a work address was asked for, and a vendor error string accepted as an email.

Delivery

Source delivered as a private repository invite within 24 hours of purchase. Single-product commercial license: use and modify in any number of products; no redistribution or resale of the source.

Interface

What you call, and what comes back. Types and signatures only — the implementation ships with the source.

  export function parseName(fullName: string):;
  export function domainFromWebsite(website: string | null | undefined): string;
  export function inferCandidates(fullName: string, domain: string): EmailCandidate[];
  export async function domainHasMx(domain: string): Promise<boolean | null>;
  export async function inferEmail(fullName: string, website: string): Promise<EmailWaterfallResult>;
  export function parseHunter(json: unknown):;
  export function hunterConfidence(score: number | null): EmailConfidence;
  export async function hunterFindEmail(fullName: string, website: string): Promise<HunterResult>;
  export function pdlWorkEmail(raw: unknown): string;
  export function pdlPhone(raw: unknown): string;

  export type EmailSource = "inferred" | "hunter" | "pdl";
  export type EmailConfidence = "guess" | "likely" | "confirmed";