/**
 * SMTP Security Handler
 * Responsible for security aspects including IP reputation checking,
 * email validation, and authentication
 */
import * as plugins from '../../../plugins.js';
import type { ISmtpAuth } from './interfaces.js';
import type { ISecurityHandler, ISmtpServer } from './interfaces.js';
/**
 * Handles security aspects for SMTP server
 */
export declare class SecurityHandler implements ISecurityHandler {
    /**
     * Reference to the SMTP server instance
     */
    private smtpServer;
    /**
     * IP reputation checker service
     */
    private ipReputationService;
    /**
     * Simple in-memory IP denylist
     */
    private ipDenylist;
    /**
     * Cleanup interval timer
     */
    private cleanupInterval;
    /**
     * Creates a new security handler
     * @param smtpServer - SMTP server instance
     */
    constructor(smtpServer: ISmtpServer);
    /**
     * Check IP reputation for a connection
     * @param socket - Client socket
     * @returns Promise that resolves to true if IP is allowed, false if blocked
     */
    checkIpReputation(socket: plugins.net.Socket | plugins.tls.TLSSocket): Promise<boolean>;
    /**
     * Validate an email address
     * @param email - Email address to validate
     * @returns Whether the email address is valid
     */
    isValidEmail(email: string): boolean;
    /**
     * Validate authentication credentials
     * @param auth - Authentication credentials
     * @returns Promise that resolves to true if authenticated
     */
    authenticate(auth: ISmtpAuth): Promise<boolean>;
    /**
     * Log a security event
     * @param event - Event type
     * @param level - Log level
     * @param details - Event details
     */
    logSecurityEvent(event: string, level: string, message: string, details: Record<string, any>): void;
    /**
     * Add an IP to the denylist
     * @param ip - IP address
     * @param reason - Reason for denylisting
     * @param duration - Duration in milliseconds (optional, indefinite if not specified)
     */
    private addToDenylist;
    /**
     * Check if an IP is denylisted
     * @param ip - IP address
     * @returns Whether the IP is denylisted
     */
    private isIpDenylisted;
    /**
     * Get the reason an IP was denylisted
     * @param ip - IP address
     * @returns Reason for denylisting or undefined if not denylisted
     */
    private getDenylistReason;
    /**
     * Clean expired denylist entries
     */
    private cleanExpiredDenylistEntries;
    /**
     * Clean up resources
     */
    destroy(): void;
}