PHP Fatal error: Call to undefined method Attendee::email() in /usr/share/roundcubemail/plugins/libkolab/lib/kolab_format_xcal.php on line 243
for an event with
<valarm>
<properties>
<action>
<text>EMAIL</text>
</action>
<summary>
<text>Alarm notification</text>
</summary>
<description>
<text>This is an event reminder</text>
</description>
<attendee>
<cal-address>mailto:%3Cjohn.crummy%40example.org%3E</cal-address>
</attendee>
<trigger>
[removed]
</trigger>
</properties>
</valarm>
Change in line 243 of kolab_format_xcal.php from $cr->email() to $cr->contact()->email() fixes the issue.