import nodemailer from 'nodemailer';
export declare class EmailProvider {
    private static _instance;
    private _smtp_transporter;
    /**
     * Return the instance of the EmailProvider.
     */
    static getInstance(): Promise<EmailProvider>;
    /**
     * Connect to MongoDB and return the database instance.
     */
    connect(): Promise<nodemailer.Transporter>;
    /**
     * Send an email.
     *
     * @param emailOptions - The email options.
     * @returns A promise that resolves when the email is sent.
     */
    send({ html, subject, to, ...options }: nodemailer.SendMailOptions): Promise<void>;
}
export declare const emailProvider: EmailProvider;