== As an administrator, what do I have to do? ==
If your're terminating SSL traffic at load balancer level, open the server.properties ( /opt/openexchange/etc/groupware/server.properties ) and set
com.openexchange.forceHTTPS=true
you may find the old option
com.openexchange.cookie.forceHTTPS already configured, in that case just rename it to com.openexchange.forceHTTPS, thereby all links generated by the backend will suggest https is used.
If your're terminating SSL traffic at load balancer level, open the server.properties ( /opt/openexchange/etc/groupware/server.properties ) and set
com.openexchange.forceHTTPS=true
you may find the old option
com.openexchange.cookie.forceHTTPS already configured, in that case just rename it to com.openexchange.forceHTTPS, thereby all links generated by the backend will suggest https is used.