/**
 * SMTP Client Connection Manager
 * Connection pooling and lifecycle management
 */
import { EventEmitter } from 'node:events';
import type { ISmtpClientOptions, ISmtpConnection, IConnectionPoolStatus } from './interfaces.js';
export declare class ConnectionManager extends EventEmitter {
    private options;
    private connections;
    private pendingConnections;
    private idleTimeout;
    constructor(options: ISmtpClientOptions);
    /**
     * Get or create a connection
     */
    getConnection(): Promise<ISmtpConnection>;
    /**
     * Create a new connection
     */
    createConnection(): Promise<ISmtpConnection>;
    /**
     * Release a connection back to the pool or close it
     */
    releaseConnection(connection: ISmtpConnection): void;
    /**
     * Close a specific connection
     */
    closeConnection(connection: ISmtpConnection): void;
    /**
     * Close all connections
     */
    closeAllConnections(): void;
    /**
     * Get connection pool status
     */
    getPoolStatus(): IConnectionPoolStatus;
    /**
     * Update connection activity timestamp
     */
    updateActivity(connection: ISmtpConnection): void;
    private establishSocket;
    private setupSocketHandlers;
    private findIdleConnection;
    private shouldReuseConnection;
    private getActiveConnectionCount;
    private getConnectionId;
    private setupIdleCleanup;
}