/**
 * Server-side issuer-selection policy, ported from the legacy gmail-listener
 * `getIssuerEmail`.
 *
 * In the v2 split (see docs/multi-tenant-gmail-listener/business-recognition-plan.md,
 * Workstream A) the gateway parses the MIME message and forwards candidate sender
 * addresses — header-derived (`from`, `replyTo`, …) plus any `From: <mailto:…>`
 * links found in the body — as sender evidence. The selection policy that decides
 * *which* address identifies the issuing business stays here, next to the
 * `suggestion_data.emails` lookup it feeds, as the single DB-adjacent source of
 * truth.
 */
export interface SenderEvidence {
    /** From header address. */
    from?: string | null;
    /** Reply-To header address. */
    replyTo?: string | null;
    /** X-Original-From / X-Original-Sender address. */
    originalFrom?: string | null;
    /** X-Forwarded-To / Envelope-To address. */
    forwardedTo?: string | null;
    /** Addresses parsed from `From: <mailto:…>` lines in the body, in document order. */
    issuerCandidates?: ReadonlyArray<string | null> | null;
}
/**
 * Pick the issuer email used for business recognition, or `null` if none can be
 * determined. Mirrors the legacy precedence:
 *
 *   1. the first body `mailto:` candidate that is either not a known provider,
 *      or — when there is no Reply-To — the first candidate regardless;
 *   2. else the first of `originalFrom` / `from` that is not a known provider;
 *   3. else `replyTo`;
 *   4. else `from`.
 */
export declare function selectIssuerEmail(evidence: SenderEvidence | null | undefined): string | null;