The YellowFox website is hosted using the urls

• map.yellowfox.de (http and https)
• map.yellowfox.info (http and https)
• api.yellowfox.net (http and https)
• api.yellowfox.info (http and https)
• cdn.yellowfox.net (http and https)
• cdn.yellowfox.info (http and https)

Depending on your used map provider you will need to add their servers as well to your ruleset.

Usually, it works best not to create rules based on domains, but based on networks. Please read this article for further information.