diff --git a/plugins/calendar/config.inc.php.dist b/plugins/calendar/config.inc.php.dist
index 99da1edc..22705b86 100644
--- a/plugins/calendar/config.inc.php.dist
+++ b/plugins/calendar/config.inc.php.dist
@@ -138,8 +138,9 @@ $config['calendar_freebusy_trigger'] = false;
 $config['calendar_include_freebusy_data'] = 1;
 
 // SMTP server host used to send (anonymous) itip messages.
-// Set to '' in order to use PHP's mail() function for email delivery.
 // To override the SMTP port or connection method, provide a full URL like 'tls://somehost:587'
+// This will add a link to invitation messages to allow users from outside
+// to reply when their mail clients do not support iTip format.
 $config['calendar_itip_smtp_server'] = null;
 
 // SMTP username used to send (anonymous) itip messages
diff --git a/plugins/libcalendaring/lib/libcalendaring_itip.php b/plugins/libcalendaring/lib/libcalendaring_itip.php
index b960e9a4..4a4e88d5 100644
--- a/plugins/libcalendaring/lib/libcalendaring_itip.php
+++ b/plugins/libcalendaring/lib/libcalendaring_itip.php
@@ -44,7 +44,6 @@ class libcalendaring_itip
             array('identity' => $this->rc->user->list_emails(true)));
         $this->sender = $hook['identity'];
 
-        $this->plugin->add_hook('message_before_send', array($this, 'before_send_hook'));
         $this->plugin->add_hook('smtp_connect', array($this, 'smtp_connect_hook'));
     }
 
@@ -152,7 +151,10 @@ class libcalendaring_itip
         // }
 
         // append links for direct invitation replies
-        if ($method == 'REQUEST' && $rsvp && ($token = $this->store_invitation($event, $recipient['email']))) {
+        if ($method == 'REQUEST' && $rsvp
+            && $this->rc->config->get('calendar_itip_smtp_server')
+            && ($token = $this->store_invitation($event, $recipient['email']))
+        ) {
             $mailbody .= "\n\n" . $this->gettext(array(
                 'name' => 'invitationattendlinks',
                 'vars' => array('url' => $this->plugin->get_url(array('action' => 'attend', 't' => $token))),
@@ -177,20 +179,6 @@ class libcalendaring_itip
         return $sent;
     }
 
-    /**
-     * Plugin hook triggered by rcube::deliver_message() before delivering a message.
-     * Here we can set the 'smtp_server' config option to '' in order to use
-     * PHP's mail() function for unauthenticated email sending.
-     */
-    public function before_send_hook($p)
-    {
-        if ($this->itip_send && !$this->rc->user->ID && $this->rc->config->get('calendar_itip_smtp_server', null) === '') {
-            $this->rc->config->set('smtp_server', '');
-        }
-
-        return $p;
-    }
-
     /**
      * Plugin hook to alter SMTP authentication.
      * This is used if iTip messages are to be sent from an unauthenticated session