declare type ResponseType = "simple" | "reason";
export interface Options {
    helo: string;
    from: string;
    to: string;
    catchalltest?: boolean;
    timeout?: number;
    responseType?: ResponseType;
}
export interface VerifyResult {
    /**
     * result code, ie. INVALID, EXIST, etc
     */
    resultCode: string;
    /**
     * reason for failure
     */
    reason?: string;
}
export declare function verify(opts: Options): Promise<string | VerifyResult>;
export declare function delay(ms: number): Promise<void>;
export {};