This .NET Email Component supports HTML email with automatic image embedding and a variety of features including authentication, message queuing, mail merge, and more. It can automatically ZIP compress attachments and supports multiple recipients and attachments.

One of the best things about Smtp.NET is that it's designed to be incredibly user friendly. Unlike other options on the market, there's no need to learn an entire object model just to send an email with Smtp.NET.
Smtp.NET comes with a wide range of features that include HTML Email with automatic image embedding, authentication, automatic ZIP compression of attachments, support for message queuing on IIS & emailQ.NET, mail merge, multiple attachments, multiple recipients, specify multiple servers for failover and redundancy, and more.
This Email Component is installed in the GAC (Global Assembly Cache) which means that all of your developers can easily access it. Additionally, Smtp.NET is packed with functionality that you won't find in the System.Web.Mail.SmtpMail class.
The best part is that Smtp.NET is fully supported and extensively documented with plenty of examples to jump-start your application development process. Plus, there are a range of royalty-free redistribution licenses, site-wide licenses, and multiple user discounts available.
Overall, if you're in need of a robust and user-friendly Email Component for ASP.NET or .NET Windows Forms, Smtp.NET is definitely worth checking out!
Version 3.0.5: Bug fixes and enhancements