Assuming you're writing a Windows application (Windows Forms, WPF, etc.), then you need to pass
a mailto:
URI[
^] to the
Process.Start
method:
System.Diagnostics.Process.Start("mailto:test@hotmail.com");
If you're writing an ASP.NET application, then you need to use a
mailto:
link to launch the email client on the user's computer, rather than on the server:
<a href="mailto:test@hotmail.com">Send an email</a>