### /etc/kopano/webapp/config-mattermost.php ### Set up Mattermost URL define('PLUGIN_MATTERMOST_URL', 'https://mattermost.'); ### Headers for Content Security, sample code in the vhost files. [...] ### Optional headers to access Mattermost from the Kopano WebApp Header set X-Frame-Options "ALLOW-FROM https://kopano./webapp/" Header edit Content-Security-Policy ^(.*)$ "$1;frame-ancestors 'self' https://kopano./webapp/" Header unset X-Frame-Options Header unset Content-Security-Policy