SendGrid is an email service provider that offers a powerful API for sending emails. To use SendGrid, you need to create an account and set up your sender email address or domain. You can then use the SendGrid .NET library to send emails with dynamic templates using the Handlebars templating language. The library provides methods such as CreateSingleEmail and CreateSingleTemplateEmail to simplify the process of sending emails with templates. To use dynamic email templates, you need to set up a template in the SendGrid dashboard and then create a C# application that uses the template ID and data to render the template. The code example provided shows how to send an email using a dynamic template with a list of todo items.