Svix is a webhooks sending service that enables developers to build secure, reliable, and scalable webhook platforms in minutes. It provides an enterprise-ready solution for sending webhooks and can be used with various email APIs, including Resend. Resend offers an email API for developers, allowing users to send emails and receive real-time alerts when emails are opened or links are clicked. The service allows users to set up webhooks, verify the signature of incoming webhooks, and send notifications to Slack. A demo showcases how to set up webhooks in Resend, receive them, verify the signature, and send a notification to Slack. The process involves creating an email template, sending emails using the template, receiving webhook messages, verifying the signature, and sending notifications to Slack.