When assigning a domain or subdomain to a folder on your webspace, Varnish Cache is activated by default for that domain or subdomain. You have the option to disable Varnish Cache for your entire account by navigating in the Control Panel to [Web Hosting], then going to [Web Server Settings] and clicking on [Manage] under Varnish.
There you can set the cache time to 0 and clear the cache. If you only want to cache certain domains or subdomains with Varnish, you can leave the global cache disabled and enable the cache in the advanced subdomain settings for the respective site.
This setting can be found under [Web Hosting], then [Subdomains], and by clicking on the [Edit Icon] for the respective [Subdomain].