You can send emails using SMS by setting up a PHP application that uses Twilio and SendGrid APIs. To start, you need to create a development environment with the required tools and packages, including PHP, Composer, Twilio, ngrok, and SendGrid. You then set up your credentials and install the necessary packages. Next, you create helper functions to process user input and send emails using SendGrid. Finally, you create a Twilio webhook to receive incoming SMS messages and process them using your application. With this setup, you can send emails using SMS even without internet access.