Build a Secure Signup API in .NET that Filters Emails and Verifies with Twilio SendGrid

The tutorial outlines a process for building a secure signup API using .NET, which blocks suspicious email domains and sends verification emails through Twilio SendGrid. It includes instructions on setting up a .NET Web API project, integrating Swagger UI for API documentation and testing, and implementing email validation using regular expressions. The guide provides steps for creating a blocklist of disposable email domains and an allowlist for specific permitted domains, enhancing security by controlling who can sign up. Additionally, it covers sending verification emails using the SendGrid API, with detailed instructions on configuring API keys and environment variables. The tutorial emphasizes implementing a robust system for ensuring user authenticity, suitable for internal tools or platforms with controlled access.