sending email error:Error: Invalid login: 454 4.7.0 Too many login attempts, please try again later. b18sm2198190pgk.36 - gsmtp

I am getting this error while sending mail through my Node js application using gmail SMTP server.

I have not reached the daily limit to send mails, my config looks like this:

var transporter = nodemailer.createTransport({
        service: 'Gmail',
        pool: true,
        port: 587,
        auth: {
            user: username,
            pass: password
        }
    });

Kindly help.

Thanks