Hi Till,
Why you've commented the line 38 (Header append Cache-Control public env=!NO_CACHE ) in changeset 2939 ( http://trac.roundcube.net/changeset/2939/trunk/roundcubemail/.htaccess)?
I'm dealing with an apache/1.3 500 error caused by this line (when active). You've commented it to prevent this error?
Thank you!