On 2 Mar 2019, at 07:13, cor@xs4all.nl wrote:
Check your server logs and your javascript console if you see any errors and report them as an issue on my plugin if you see any.
There were no errors in roundcube/errors and I did not check the JavaScript console at the time, however this appears to be an issue in my test Roundcube and not tied to message-highlight at all. It looks like because the test server is set to X-Frame-Options DENY the settings and preview cannot work. These settings are not used on the live subdomain for Roundcube and I mistakenly ascribed this issue to adding the plugin.
Goops.