安装 kolab 提供的 roundcube 插件
https://git.kolab.org/diffusion/RPK/browse/master/plugins/
- https://git.kolab.org/diffusion/RPK/browse/master/plugins/calendar/
- https://git.kolab.org/diffusion/RPK/browse/master/plugins/kolab_2fa/
- https://git.kolab.org/diffusion/RPK/browse/master/plugins/kolab_activesync/
- https://git.kolab.org/diffusion/RPK/browse/master/plugins/kolab_addressbook/
- https://git.kolab.org/diffusion/RPK/browse/master/plugins/tasklist/
- https://git.kolab.org/diffusion/RPK/browse/master/plugins/kolab_notes/