I dunno if this helps, but I got a tiny site up that uses your settings here: http://www.taikyuu.com.sg/contact.aspx
Here's my staged settings:
<?xml version="1.0"?>
<!--
A full list of settings and comments can be found in
machine.config.comments usually located in
\Windows\Microsoft.Net\Framework\v2.x\Config
-->
<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
<appSettings>
<add key="EmailTo" value="sales [at] blahblahblah.com.sg" />
<add key="EmailSubject" value="Customer Enquiry / Request For Information" />
</appSettings>
<system.net>
<mailSettings>
<smtp>
<network host="mailmx.blahblahblah.com.sg" defaultCredentials="false" />
</smtp>
</mailSettings>
</system.net>
<system.web>
<!-- Set default masterpage -->
<pages masterPageFile="~/Default.master" />
<!--
Set compilation debug="true" to insert debugging
symbols into the compiled page. Because this
affects performance, set this value to true only
during development.
-->
<compilation debug="false"/>
<!--
The <authentication> section enables configuration
of the security authentication mode used by
ASP.NET to identify an incoming user.
-->
<authentication mode="None"/>
<!--
The <customErrors> section enables configuration
of what to do if/when an unhandled error occurs
during the execution of a request. Specifically,
it enables developers to configure html error pages
to be displayed in place of a error stack trace.
<customErrors mode="RemoteOnly" defaultRedirect="GenericErrorPage.htm">
<error statusCode="403" redirect="NoAccess.htm"/>
<error statusCode="404" redirect="FileNotFound.htm"/>
</customErrors>
-->
</system.web>
</configuration>