最后.

这有效:

<rule name="redirect diamonds" stopProcessing="true">
            <match url="^diamonds/diamondrings" ignoreCase="true" />
            <conditions>
                <add input="{HTTP_HOST}" pattern="^(www.)?mywebshop.azurewebsites.net" />
            </conditions>
            <action type="Redirect" url="/diamondrings" redirectType="Permanent" />
        </rule>