diff --git a/plugins/calendar/calendar_ui.js b/plugins/calendar/calendar_ui.js
index b99d4e49..a99ec4f1 100644
--- a/plugins/calendar/calendar_ui.js
+++ b/plugins/calendar/calendar_ui.js
@@ -2562,7 +2562,15 @@ function rcube_calendar_ui(settings)
       if (_has_attendees) {
         var checked = (settings.itip_notify & 1 ? ' checked="checked"' : '');
 
-        if (_is_organizer) {
+        if (action == 'remove' && cal.group == 'personal' && is_attendee(event)) {
+          decline = true;
+          checked = event.status != 'CANCELLED' ? checked : '';
+          html += '<div class="message">' +
+            '<label><input class="confirm-attendees-decline" type="checkbox"' + checked + ' value="1" name="decline" />&nbsp;' +
+            rcmail.gettext('itipdeclineevent', 'calendar') + 
+            '</label></div>';
+        }
+        else {
           notify = true;
           if (settings.itip_notify & 2) {
             html += '<div class="message">' +
@@ -2574,17 +2582,6 @@ function rcube_calendar_ui(settings)
             data._notify = settings.itip_notify;
           }
         }
-        else if (action == 'remove' && is_attendee(event)) {
-          decline = true;
-          checked = event.status != 'CANCELLED' ? checked : '';
-          html += '<div class="message">' +
-            '<label><input class="confirm-attendees-decline" type="checkbox"' + checked + ' value="1" name="decline" />&nbsp;' +
-            rcmail.gettext('itipdeclineevent', 'calendar') + 
-            '</label></div>';
-        }
-        else {
-          html += '<div class="message">' + rcmail.gettext('localchangeswarning', 'calendar') + '</div>';
-        }
       }
 
       // recurring event: user needs to select the savemode
diff --git a/plugins/libcalendaring/lib/libcalendaring_itip.php b/plugins/libcalendaring/lib/libcalendaring_itip.php
index c7986175..41a5c825 100644
--- a/plugins/libcalendaring/lib/libcalendaring_itip.php
+++ b/plugins/libcalendaring/lib/libcalendaring_itip.php
@@ -261,6 +261,21 @@ class libcalendaring_itip
             }
         }
 
+        // Set SENT-BY property if the sender is not the organizer
+        if ($method == 'CANCEL' || $method == 'REQUEST') {
+            foreach ((array)$event['attendees'] as $idx => $attendee) {
+                if ($attendee['role'] == 'ORGANIZER'
+                    && $attendee['email']
+                    && strcasecmp($attendee['email'], $from) != 0
+                    && strcasecmp($attendee['email'], $from_utf) != 0
+                ) {
+                    $attendee['sent-by'] = 'mailto:' . $from_utf;
+                    $event['organizer'] = $event['attendees'][$idx] = $attendee;
+                    break;
+                }
+            }
+        }
+
         // compose multipart message using PEAR:Mail_Mime
         $message = new Mail_mime("\r\n");
         $message->setParam('text_encoding', 'quoted-printable');
diff --git a/plugins/libcalendaring/libvcalendar.php b/plugins/libcalendaring/libvcalendar.php
index b47cf81e..78a9e2c1 100644
--- a/plugins/libcalendaring/libvcalendar.php
+++ b/plugins/libcalendaring/libvcalendar.php
@@ -45,6 +45,12 @@ class libvcalendar implements Iterator
         'delegated-from'  => 'DELEGATED-FROM',
         'delegated-to'    => 'DELEGATED-TO',
         'schedule-status' => 'SCHEDULE-STATUS',
+        'sent-by'         => 'SENT-BY',
+    );
+    private $organizer_keymap = array(
+        'name'            => 'CN',
+        'schedule-status' => 'SCHEDULE-STATUS',
+        'sent-by'         => 'SENT-BY',
     );
     private $iteratorkey = 0;
     private $charset;
@@ -1173,7 +1179,7 @@ class libvcalendar implements Iterator
 
         if ($event['organizer']) {
             $ve->add('ORGANIZER', 'mailto:' . $event['organizer']['email'],
-                array_filter(self::map_keys($event['organizer'], array('name' => 'CN', 'schedule-status' => 'SCHEDULE-STATUS'))));
+                array_filter(self::map_keys($event['organizer'], $this->organizer_keymap)));
         }
 
         foreach ((array)$event['url'] as $url) {