/**
 * SMTP Client TLS Handler
 * TLS and STARTTLS client functionality
 */
import * as tls from 'node:tls';
import type { ISmtpConnection, ISmtpClientOptions } from './interfaces.js';
import type { CommandHandler } from './command-handler.js';
export declare class TlsHandler {
    private options;
    private commandHandler;
    constructor(options: ISmtpClientOptions, commandHandler: CommandHandler);
    /**
     * Upgrade connection to TLS using STARTTLS
     */
    upgradeToTLS(connection: ISmtpConnection): Promise<void>;
    /**
     * Create a direct TLS connection
     */
    createTLSConnection(host: string, port: number): Promise<tls.TLSSocket>;
    /**
     * Validate TLS certificate
     */
    validateCertificate(socket: tls.TLSSocket): boolean;
    /**
     * Get TLS connection information
     */
    getTLSInfo(socket: tls.TLSSocket): any;
    /**
     * Check if TLS upgrade is required or recommended
     */
    shouldUseTLS(connection: ISmtpConnection): boolean;
    private performTLSUpgrade;
}