Sending bulk mail using nodemailer without others knowing all recipients?

Question

I am trying to build a bulk mailer service which could send campaign emails to all the list of users. Everything works fine, when I import the user emails from json file and add it to to section in nodemailer transport object.

Something like this below:-

// send mail with defined transport object
const message = {
    from: `${process.env.FROM_NAME} <${process.env.FROM_EMAIL}>`,
    to: options.email,
    subject: options.subject,
    text: options.message,
};

Here options.email is a array of all emails of registered users.
Now the problem is, that the received users can see that who else have received the email as CC. I tried using BCC but I cannot leave to object empty. I need a way to send bulk email where receivers won't know who else have got the email.

Please Help and thankyou in advance.