export interface SmtpClientOptions {
    host: string;
    port?: number;
}
export interface SmtpClientResponse {
    code: number;
    message: string;
}
export declare class SmtpClient {
    private options;
    private client?;
    private queue;
    private debug;
    constructor(options: SmtpClientOptions);
    connect(): Promise<SmtpClientResponse>;
    close(): void;
    helo(value: string): Promise<SmtpClientResponse>;
    from(value: string): Promise<SmtpClientResponse>;
    to(value: string): Promise<SmtpClientResponse>;
    private write;
    private read;
}