Building a multi-channel notification service using AWS involves leveraging Amazon Simple Email Service (SES) and Amazon Simple Notification Service (SNS) to cater to diverse user communication preferences. This approach is particularly beneficial for companies already utilizing AWS infrastructure, as it allows seamless integration with existing systems and familiarity with AWS APIs. The architecture involves creating a standalone notification service with functionalities such as templating, error handling, user preferences, and notification routing, all of which enhance user engagement by delivering tailored notifications. While AWS provides foundational APIs for notifications, developers must implement additional features like error-checking, contact management, and advanced templating to overcome the "rawness" of AWS services. To streamline these processes, services like Courier offer enhanced solutions with features like a Notification Designer, automated handling of errors and unsubscribes, and integration with multiple providers, making it easier to manage and scale notification systems without extensive development effort.