If you're interested in a third party solution, we provide an SMTP component for the .NET Compact Framework in our IP*Works! .NET CF toolkit. The component is fairly simply to use:
We provide the SMTP component in a toolkit of 34 internet components, all fully managed C# with no dependancies, including a FileMailer and HTMLMailer component. These components use SMTP internally, but also handle the MIME encoding of attachments or HTML automatically, making more complex emails much easier to send.
We provide a fully functional trial version of the toolkit at our website at http://www.nsoftware.com/download/. The only restriction is an about box that appears in your applications, reminding you to register before you go on to deployment.
If you don't want a third-party solution, you're going to be writing your
own first-party solution. Fortunately, SMTP isn't a very complicated
protocol...