new: [mail] Add reference for event alert emails

app/Lib/Tools/SendEmail.php

@@ -441,15 +441,25 @@ class SendEmail
         if ($body instanceof SendEmailTemplate) {
             $body->set('canEncryptSmime', $canEncryptSmime);
             $body->set('canEncryptGpg', $canEncryptGpg);
-            $body = $body->render($hideDetails);
+            $bodyContent = $body->render($hideDetails);
         } else {
             if ($hideDetails && $bodyWithoutEncryption) {
                 $body = $bodyWithoutEncryption;
             }
-            $body = new CakeEmailBody($body);
+            $bodyContent = new CakeEmailBody($body);
         }
 
-        $email = $this->create($user, $subject, $body, [], $replyToUser);
+        $email = $this->create($user, $subject, $bodyContent, [], $replyToUser);
+
+        // Generate `In-Reply-To` and `References` to group emails
+        if ($body instanceof SendEmailTemplate && $body->referenceId()) {
+            $reference = sha1($body->referenceId() . '|' .  Configure::read('MISP.uuid'));
+            $reference = "<$reference@{$email->domain()}>";
+            $email->addHeaders([
+                'In-Reply-To' => $reference,
+                'References' => $reference,
+            ]);
+        }
 
         $signed = false;
         if (Configure::read('GnuPG.sign')) {

app/Lib/Tools/SendEmailTemplate.php

@@ -7,12 +7,29 @@ class SendEmailTemplate
     /** @var string */
     private $viewName;
 
+    /** @var string|null */
+    private $referenceId;
+
     public function __construct($viewName)
     {
         $this->viewName = $viewName;
     }
 
     /**
+     * This value will be used for grouping emails in mail client.
+     * @param string|null $referenceId
+     * @return string
+     */
+    public function referenceId($referenceId = null)
+    {
+        if ($referenceId === null) {
+            return $this->referenceId ;
+        }
+        $this->referenceId = $referenceId;
+    }
+
+    /**
+     * Set template variable.
      * @param string $key
      * @param mixed $value
      */
@@ -29,6 +46,7 @@ class SendEmailTemplate
     public function render($hideDetails = false)
     {
         $View = new View();
+        $View->autoLayout = false;
         $View->helpers = ['TextColour'];
         $View->loadHelpers();
 

app/Model/Event.php

@@ -3247,6 +3247,7 @@ class Event extends AppModel
         $template->set('distributionLevels', $this->distributionLevels);
         $template->set('analysisLevels', $this->analysisLevels);
         $template->set('tlp', $this->getEmailSubjectMarkForEvent($event));
+        $template->referenceId("event-alert|{$event['Event']['id']}");
         return $template;
     }