diff --git a/admin/tool/messageinbound/classes/manager.php b/admin/tool/messageinbound/classes/manager.php
index dcb4e7bc7ea..7e1236761aa 100644
--- a/admin/tool/messageinbound/classes/manager.php
+++ b/admin/tool/messageinbound/classes/manager.php
@@ -295,6 +295,11 @@ class manager {
         // First flag this message to prevent another running hitting this message while we look at the headers.
         $this->add_flag_to_message($messageid, self::MESSAGE_FLAGGED);
 
+        if ($this->is_bulk_message($message, $messageid)) {
+            mtrace("- The message has a bulk header set. This is likely an auto-generated reply - discarding.");
+            return;
+        }
+
         // Record the user that this script is currently being run as.  This is important when re-processing existing
         // messages, as cron_setup_user is called multiple times.
         $originaluser = $USER;
@@ -741,6 +746,43 @@ class manager {
         return in_array($flag, $flags);
     }
 
+    /**
+     * Attempt to determine whether this message is a bulk message (e.g. automated reply).
+     *
+     * @param \Horde_Imap_Client_Data_Fetch $message The message to process
+     * @param string|\Horde_Imap_Client_Ids $messageid The Hore message Uid
+     * @return boolean
+     */
+    private function is_bulk_message(
+            \Horde_Imap_Client_Data_Fetch $message,
+            $messageid) {
+        $query = new \Horde_Imap_Client_Fetch_Query();
+        $query->headerText(array('peek' => true));
+
+        $messagedata = $this->client->fetch($this->get_mailbox(), $query, array('ids' => $messageid))->first();
+
+        // Assume that this message is not bulk to begin with.
+        $isbulk = false;
+
+        // An auto-reply may itself include the Bulk Precedence.
+        $precedence = $messagedata->getHeaderText(0, \Horde_Imap_Client_Data_Fetch::HEADER_PARSE)->getValue('Precedence');
+        $isbulk = $isbulk || strtolower($precedence) == 'bulk';
+
+        // If the X-Autoreply header is set, and not 'no', then this is an automatic reply.
+        $autoreply = $messagedata->getHeaderText(0, \Horde_Imap_Client_Data_Fetch::HEADER_PARSE)->getValue('X-Autoreply');
+        $isbulk = $isbulk || ($autoreply && $autoreply != 'no');
+
+        // If the X-Autorespond header is set, and not 'no', then this is an automatic response.
+        $autorespond = $messagedata->getHeaderText(0, \Horde_Imap_Client_Data_Fetch::HEADER_PARSE)->getValue('X-Autorespond');
+        $isbulk = $isbulk || ($autorespond && $autorespond != 'no');
+
+        // If the Auto-Submitted header is set, and not 'no', then this is a non-human response.
+        $autosubmitted = $messagedata->getHeaderText(0, \Horde_Imap_Client_Data_Fetch::HEADER_PARSE)->getValue('Auto-Submitted');
+        $isbulk = $isbulk || ($autosubmitted && $autosubmitted != 'no');
+
+        return $isbulk;
+    }
+
     /**
      * Send the message to the appropriate handler.
      *
diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index bef85967a28..40633b7ef08 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -735,12 +735,16 @@ function forum_cron() {
 
                 $userfrom->customheaders = array (
                     // Headers to make emails easier to track.
-                    'Precedence: Bulk',
                     'List-Id: "'        . $cleanforumname . '" <moodleforum' . $forum->id . '@' . $hostname.'>',
                     'List-Help: '       . $CFG->wwwroot . '/mod/forum/view.php?f=' . $forum->id,
                     'Message-ID: '      . forum_get_email_message_id($post->id, $userto->id, $hostname),
                     'X-Course-Id: '     . $course->id,
-                    'X-Course-Name: '   . format_string($course->fullname, true)
+                    'X-Course-Name: '   . format_string($course->fullname, true),
+
+                    // Headers to help prevent auto-responders.
+                    'Precedence: Bulk',
+                    'X-Auto-Response-Suppress: All',
+                    'Auto-Submitted: auto-generated',
                 );
 
                 if ($post->parent) {
@@ -1055,7 +1059,12 @@ function forum_cron() {
                             }
                         }
 
-                        $userfrom->customheaders = array ("Precedence: Bulk");
+                        // Headers to help prevent auto-responders.
+                        $userfrom->customheaders = array(
+                                "Precedence: Bulk",
+                                'X-Auto-Response-Suppress: All',
+                                'Auto-Submitted: auto-generated',
+                            );
 
                         $maildigest = forum_get_user_maildigest_bulk($digests, $userto, $forum->id);
                         if ($maildigest == 2) {