Have a look at
this[
^] awesome article.
In particular, lower down in the article, have a look at the app settings defined as below
value="Application/Context/Cookie/QueryString/Off" />
<add key="customErrorPage" value="myErrorPage.aspx" />
<add key="customErrorBranchMethod" value="Redirect/Transfer" />
<add key="customErrorAllowReport" value="On/Off" />
<add key="customErrorEmailAddress" value="errors@mySite.com</pre></xml>"></add>