npm install nodemailer

import nodemailer from 'nodemailer';
import { Options } from 'nodemailer/lib/smtp-transport';

export type SendMailOptions = nodemailer.SendMailOptions; 

/**
 * SMTP Client
 *
 * @export
 * @class Smtp
 */
export class Smtp {
    /** SMTP設定 */
    private options: Options;
    /** email 轉運器 */
    private transporter: nodemailer.Transporter;

    /**
     *Creates an instance of Smtp.
     * @param {string} account 帳號(寄件者信箱)
     * @param {string} password 密碼
     * @memberof Smtp
     */
    constructor(account: string = process.env.SMTP_ACCOUNT, password: string = process.env.SMTP_PASSWORD) {
        this.options = {
            host: process.env.SMTP_HOST,
            port: process.env.SMTP_PORT,
            secure: process.env.SMTP_PORT === 465 ? true : false,
            tls: {
                rejectUnauthorized: false,
            }
        };
        if (account) {
            this.options.auth = {
                user: account,
                pass: password
            }                
        }
        this.transporter = nodemailer.createTransport(this.options);
        this.transporter.verify((error, success) => {
            if (success) { console.log('Server is ready to take our message');}
            else { console.log(error); }
        });
        
    }

    /**
     * 寄送mail
     *
     * @param {nodemailer.SendMailOptions} mail email內容
     * @memberof Smtp
     */
    async send(mail: SendMailOptions): Promise<boolean> {
        const isSended: Promise<boolean> = new Promise((resolve) => {
            this.transporter.sendMail(mail, (error, info) => {
                if(error) {
                    console.log(`Error: ${error}`);
                    return resolve(false);
                }
                else {
                    console.log(`Email sent: ${info.response}`)
                    return resolve(true);
                }
            });
        });

        return isSended;
    }
}