How to Send Emails in ASP.NET Core using SMTP or Email API: Mailkit and FluentMail Tutorial

ASP.NET Core applications can send email through MailKit, FluentEmail, the built-in SMTP client, or an email API, with the same underlying approach applicable to MVC and Web API projects. The walkthrough describes creating Web API projects, optionally using Swagger UI for testing, storing SMTP or API credentials in configuration files, binding settings to typed classes, registering reusable services through dependency injection, and exposing controller endpoints for requests. MailKit is presented as a feature-rich option for high-volume use cases, FluentEmail as a simpler provider-flexible abstraction, SMTP as a direct traditional method, and Mailtrap’s API as an HTTP-based alternative that can reduce manual protocol handling. Each approach can support plain-text and HTML messages, attachments, multiple recipients, embedded images, asynchronous delivery, and bulk sending, with attachments typically handled as uploaded streams or base64 API payloads and embedded images sent through content IDs or inline resources. The examples emphasize configuring sender credentials securely, using transactional versus bulk sending streams where appropriate, and adapting request models and services to the desired message format and recipient structure.

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