如何使用Node.js从用户帐户发送电子邮件？

Question

i'm working in a program that saves contacts. I want to add a new fuction that lets you send emails to your contacts form your email account. I tried to do it with nodemailer, taking the login data from a form that users need to fill in.

But nodemailer sends me a error, look this:

Error: Invalid login: 535-5.7.8 Username and Password not accepted.

I tried with applcation password and activating the less secure option, but the error continues. Look my code:

Here i take the user's email and password:

router.post('/email', isLoggedIn, async (req, res) => {
    var { email } = req.body;
    var { password } = req.body;

    var parts = email.substring(email.lastIndexOf('@')+ 1);



    exports.email = email;
    exports.password = password;

    res.redirect('/links/message')



});

Here i take de message:

router.post('/sendmessage', isLoggedIn, async (req, res) => {

    const { message } = req.body;
    const { assumpt } = req.body;
    exports.message = message;
    exports.assumpt = assumpt;
    res.redirect('/links/contactsemail')


});

Finally, i take the category contact that you need to send the email and i send the email with the message and data login that users give me:

router.post('/contactsend', isLoggedIn, async (req, ress) => {
    const { contacts } = req.body;
    const row = await pool.query('SELECT count(email) AS email FROM links WHERE user_id=? AND category=? AND email IS NOT NULL',[req.user.id, contacts]);
    const rows = row[0].email;
    const assumpt = myModule.assumpt;
    const message = myModule.message;
    const email = myModule.email;
    const password = myModule.password
    var parts = email.substring(email.lastIndexOf('@')+ 1);
    const hosts = 'smtp.' + parts;
    var transporter = nodemailer.createTransport({
        host: hosts,
        port: 587,
        auth: {
            user: email,
            pass: password
        }
    });


   for (i = 1; i <= rows; i++ ){
    var email1 = await pool.query('SELECT email AS email FROM (SELECT  email, ROW_NUMBER() OVER (ORDER BY email) AS rn FROM links WHERE user_id= ? AND category=?) q WHERE  rn = ?', [req.user.id, contacts, i]);
    var email1 = email1[0].email;
    var mailOptions = {
        from: email,
        to: email1,
        subject: assumpt,
        text: message

    };



        transporter.sendMail(mailOptions, function (error, info) {
            if (error) {
                console.log(error);

            } else {
                console.log('Email sent: ' + info.response);
                res.flash('success', 'Missatge enviat correctament');
                res.redirect('/links');
            }
        });


    };


});

My questions are:

How can I fix the error?

I can do it in different way that's it's easier and better?

Answer 1

Am I understanding this correctly that you want your users to enter their credentials for their private/external e-mail provider so you can send an e-mail using that provider?

In that case there is no generic answer to your question since the specifics of the required configuration highly depends on the e-mail provider. For example in your code:

    var parts = email.substring(email.lastIndexOf('@')+ 1);
    const hosts = 'smtp.' + parts;
    var transporter = nodemailer.createTransport({
        host: hosts,
        port: 587,
        auth: {
            user: email,
            pass: password
        }
    });

This block already has some hard-coded assumptions, ie that the smtp host for john.doe@example.net is smtp.example.org and that the username for that e-mail is also john.doe@example.net which - both - is not necessarily the case for many e-mail providers.

So even if this would work for you it is very likely it won't work for all of your users !

Instead you should use a single smtp gateway/relay your application can forward e-mails to. Then you also won't need the credentials of the users themselves but can use the login credentials for your application to that smtp gateway.

But it depends on the configuration of your smtp gateway whether you'll be allow to send with arbitrary sender addresses. And even if your gateway might allow this the mails may be blocked due to spam filters since your gateway may not be allowed to send e-mails for the users' domain, see SPF .

Therefor I would advise you - besides using a dedicated smtp gateway - to send with an e-mail address/domain you own and control. You may still augment the mail coming directly from the user, eg by setting the display name and Reply-To header appropriately:

From: "John Doe" <myapp@example.com>
To: jane.doe@example.org
Reply-To: "John Doe" <john.doe@example.org>
Subject: "A message from John Doe via MyApp"

For this mail the recipient would get the sending user's name displayed as sender (but your app's e-mail and not the user's) and when hitting the reply button the reply would by default - depending on the e-mail client - be sent back to the user, ie in this case john.doe@example.org .