When the recipient is infocenter then place a * close to the drop down description and a note under the tinymce box.

application/models/CL/Messages_model.php

@@ -88,7 +88,7 @@ class Messages_model extends CI_Model
 				$ouOptions .= sprintf(
 					"\n".'<option value="%s">%s</option>',
 					is_numeric($ou->prestudent_id) ? $ou->oe_kurzbz : self::ALT_OE,
-					$ou->bezeichnung
+					$ou->bezeichnung . (is_numeric($ou->prestudent_id) ? '' : ' *')
 				);
 			}
 		}

application/views/system/messages/ajaxWrite.php

@@ -56,6 +56,12 @@
 						<div class="col-lg-12">
 							<label><?php echo $this->p->t('ui', 'message'); ?>:</label>
 							<textarea id="body"></textarea>
+
+							<br>
+
+							<div>
+								<?php echo $this->p->t('ui', 'altRecipientNote'); ?>
+							</div>
 						</div>
 					</div>
 					<br>