diff --git a/plugins/libkolab/README b/plugins/libkolab/README
index b44d4d2b..0a3c0ce3 100644
--- a/plugins/libkolab/README
+++ b/plugins/libkolab/README
@@ -38,3 +38,6 @@ $rcmail_config['kolab_cache'] = true;
 // Defaults to https://<imap-server->/freebusy
 $rcmail_config['kolab_freebusy_server'] = 'https://<some-host>/<freebusy-path>';
 
+// Set this option to disable SSL certificate checks when triggering Free/Busy (enabled by default)
+$rcmail_config['kolab_ssl_verify_peer'] = false;
+
diff --git a/plugins/libkolab/lib/kolab_storage_folder.php b/plugins/libkolab/lib/kolab_storage_folder.php
index 5f6d2899..da0718a8 100644
--- a/plugins/libkolab/lib/kolab_storage_folder.php
+++ b/plugins/libkolab/lib/kolab_storage_folder.php
@@ -737,7 +737,9 @@ class kolab_storage_folder
         require_once('HTTP/Request2.php');
 
         try {
+            $rcmail = rcube::get_instance();
             $request = new HTTP_Request2($url);
+            $request->setConfig(array('ssl_verify_peer' => $rcmail->config->get('kolab_ssl_verify_peer', true)));
 
             // set authentication credentials
             if ($auth_user && $auth_passwd)