If you get error like "Unable to relay ..." while sending email you should do the following: open properties of your default SMTP server, select "Access" tab, click on "Relay" button under "Relay restrictions" group, switch radio list to "All except the list below' as shown at followed screenshot.

To enable IIS to work with custom .Net Url Rewrite module it's needed to do following: open "Properties" of web site -> "Home Directory" tab -> "Configuration" button. Click on "Insert" button which is located under "Wildcard application maps" label. You should point "Executable" to aspnet_isapi.dll and clear "Verify that file exists" checkbox.

For debugging it is very useful to use followed code in Global.asax:

void Application_Error(object sender, EventArgs e)
{
    System.Diagnostics.Debugger.Break();
}

But if you deploy it on IIS then in case of unhandled exception the followed dialog window will be shown for current logged on user:

The solution is to remove System.Diagnostics.Debugger.Break(); from code before deploying.