declare type MailSettings = {
    smtpHostString: string;
    smtpPort: number;
    password: string;
    sender: string;
};
export declare class MailUtil {
    private transporter;
    private settings;
    private static instance;
    static getInstance(): MailUtil;
    constructor(settings: MailSettings);
    sendMail(options: {
        to: string;
        subject: string;
        text: string;
    }): Promise<void>;
}
export {};