This rule will redirect everything from this-sub.example.com
to example.com
<rule name="My redirection home" stopProcessing="true">
<match url=".*" />
<conditions>
<add input="{HTTP_HOST}" pattern="^this-sub\." />
</conditions>
<action type="Redirect" url="http://example.com" appendQueryString="false" redirectType="Permanent" />
</rule>