/**
 * Email thread tracking utilities
 *
 * Uses standard email headers (References, In-Reply-To) to track conversation threads.
 * Follows RFC 5322 guidelines for message threading.
 */
import type { ParsedEmail } from "./types.js";
/**
 * Build a thread ID from email headers
 * Uses the first References entry, then In-Reply-To, then current Message-ID
 * @param email - Parsed email object
 * @returns Thread ID (root Message-ID)
 */
export declare function buildThreadId(email: ParsedEmail): string;
/**
 * Extract thread references for reply headers
 * @param messageId - Current message ID to add
 * @param existingReferences - Existing references array
 * @returns References array for reply, capped at 10 (root + last 9)
 */
export declare function buildReplyReferences(messageId: string, existingReferences: string[]): string[];