If you set the "show webspace content" option for a domain or subdomain, the varnish cache will be enabled by default for this site. You can disable the varnish cache for your whole account at easyname by going to your controlpanel and navigating to [Web Hosting] then to [Web Server Settings] and under Varnish click on [Manage](pen icon).
Here you can set 0 for the cache minutes or flush the data from the cache. If you only want to cache certain domains or subdomains, you can leave this option disabled and enable the varnish cache only for a specific site.
By navigating to the advanced subdomain settings which can be found here:[Web Hosting] then to [Subdomains] and at the [respective subdomain] by clicking on [edit](pen icon) "Settings »" when you choose the option "show webspace content". You can set the cache minutes now. If you set a higher value, it may take longer to update if you make changes to the website.