How to connect RoundCube to a Calendar


RoundCube is excellent Webmail but doesn’t have a calender – something people used to Outlook may require.

Fortunately the makers of RoundCube, namely Kolab, have an excellent Calendar plugin for their webmail.

Just one problem – it doesn’t come with instructions and it’s rather technical to install.

Fortunately by the Magic of Google and some blood, sweat, and tears, we were able to get it working. To follow these instructions you need to be a fairly confident sysadmin that knows how to navigate a file system and edit configuration files. How to turn on PHP error logging. Where to find those log files.

Most of the instructions were taken from anther outdated article here, modified to bring it up to date with 2021. Also we’re using Ubuntu not CentOS for this guide, although doing in on CentOS should be fairly similar.

If you’re not technical enough, you could just purchase the plugin from RoundCube plus or Kolab. See references for one possible solution.


  • You have to know where Roundcube is installed. E.g.: /home/
  • If your web server isn’t reporting PHP errors, you’re in for the long haul. If this procedure doesn’t work then you might get a 500 error and if the normal Apache/NGINX log doesn’t spit out the exact message you have a problem. Fixing PHP not logging errors is outside of the scope of this article but we’ve left advanced users one tip later in this article.
  • You need to know how to retrieve your MySQL credentials from the existing Roundcube
  • Elastic Skin must be selected in RoundCube
  • `apt install node-less` for the lessc compiler
  • Compiling of less assets
  • Removing of Dark mode switch in the less asset.
  • Adding a config for Calendar in the main include.


Here are the instructions

apt install git php-sabre-*
cd /tmp
git clone
[find your webmail installation] or [cd /usr/share/roundcube/plugins]
cp -r /tmp/RPK/plugins/calendar .
cp -r /tmp/RPK/plugins/libcalendaring .
cp -r /tmp/RPK/plugins/libkolab .
cd calendar [your actual new folder]

Edit to fit your needs but when we did it all defaults were good.

Config.php (in Main installation)

You have to calendar after copying the three directories as specified above:

// List of active plugins (in plugins/ directory)
$config['plugins'] = array('virtuser_file',

Edit the file mysql.initial.sql and the line that import system change to single backtick system single backtick

mysql -u root -pYOURPASSWORD roundcubedb < drivers/database/SQL/mysq.initial.sql


Error 500

Well sorry 500 is server error so you need more granular logging. Enable PHP ini for errors. This worked for us:


We added this to calendar.php init() function which allowed us to see that libkolab wasn’t present. So we modified the original instructions from that site to include libkolab


The source article it refers to patching libcalendaring but to us it looked like it’s a more modern version of PHP and not needed.


Unable to find CALDAV Url? You are not alone!

This most like indicates that you don’t have a CALDAV server, like WHM, who uses Apple’s CALDAV server, long ago deprecated.

Distorted Layout

Even though the calendar works, for some reason none of the list of calendar’s are showing. Please leave us a comment if you know how to fix this.


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2 thoughts on “How to connect RoundCube to a Calendar”

  1. Thanks for this article.
    I don’t use any database with roundcube.
    Is there a way to do so with calendar plugin?

    1. Eugène van der Merwe

      Hi @Nathan,

      I spent many hours trying to get it working. It’s too complicated. So far our ideas are:

      – Use Outlook instead (expensive)
      – Use Google Workspace
      – Use Kopano
      – Use WHM (but still lots of extra work)

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