To add email notifications to your Node.js SMS app using Twilio and SendGrid, you'll need to install the required dependencies, set up your accounts with Twilio and SendGrid, and then integrate the SendGrid library into your application. You can use the same codebase for both sending emails and SMS messages, and customize the notification content and delivery method according to your requirements. By following these steps, you can enhance the user experience of your app by providing personalized and timely notifications that cater to individual preferences.