We are trying to add a custom header (X-Robots-Tag) for sitemap files in IIS 7.5. However, it does not appear that IIS supports custom headers based on a file type or wildca
You can use the IIS UrlRewrite module and add a custom outbound rule to configure the custom header. Here is a sample rule you may want to use:
<system.webServer>
<rewrite>
<outboundRules>
<rule name="Set custom HTTP response header">
<match serverVariable="RESPONSE_X_Robots_Tag" pattern=".*" />
<conditions>
<add input="{REQUEST_URI}" pattern="\.xml\.gz$" />
</conditions>
<action type="Rewrite" value="The value you need for this header"/>
</rule>
</outboundRules>
</rewrite>
</system.webServer>
More info: UrlRewrite documentation