diff --git a/mailpoet/lib/API/JSON/ResponseBuilders/NewslettersResponseBuilder.php b/mailpoet/lib/API/JSON/ResponseBuilders/NewslettersResponseBuilder.php
index c261aa3182..98b45207b2 100644
--- a/mailpoet/lib/API/JSON/ResponseBuilders/NewslettersResponseBuilder.php
+++ b/mailpoet/lib/API/JSON/ResponseBuilders/NewslettersResponseBuilder.php
@@ -113,7 +113,10 @@ class NewslettersResponseBuilder {
     return $data;
   }
 
-  private function processPersonalizationTags(string $content): string {
+  private function processPersonalizationTags(?string $content): ?string {
+    if (is_null($content) || strlen($content) === 0) {
+      return $content;
+    }
     if (strpos($content, '<!--') === false) {
       // we don't need to parse anything if there are no personalization tags
       return $content;
@@ -278,7 +281,7 @@ class NewslettersResponseBuilder {
       'meta' => $queue->getMeta(),
       'task_id' => (string)$task->getId(), // (string) for BC
       'newsletter_id' => ($newsletter = $queue->getNewsletter()) ? (string)$newsletter->getId() : null, // (string) for BC
-      'newsletter_rendered_subject' => $queue->getNewsletterRenderedSubject(),
+      'newsletter_rendered_subject' => $this->processPersonalizationTags($queue->getNewsletterRenderedSubject()),
       'count_total' => (string)$queue->getCountTotal(), // (string) for BC
       'count_processed' => (string)$queue->getCountProcessed(), // (string) for BC
       'count_to_process' => (string)$queue->getCountToProcess(), // (string) for BC
diff --git a/mailpoet/tests/integration/API/JSON/ResponseBuilders/NewslettersResponseBuilderTest.php b/mailpoet/tests/integration/API/JSON/ResponseBuilders/NewslettersResponseBuilderTest.php
index 7ac6bd2629..ac96a98f61 100644
--- a/mailpoet/tests/integration/API/JSON/ResponseBuilders/NewslettersResponseBuilderTest.php
+++ b/mailpoet/tests/integration/API/JSON/ResponseBuilders/NewslettersResponseBuilderTest.php
@@ -5,6 +5,8 @@ namespace MailPoet\API\JSON\ResponseBuilders;
 use Codeception\Util\Stub;
 use MailPoet\DI\ContainerWrapper;
 use MailPoet\Entities\NewsletterEntity;
+use MailPoet\Entities\ScheduledTaskEntity;
+use MailPoet\Entities\SendingQueueEntity;
 use MailPoet\Logging\LogRepository;
 use MailPoet\Newsletter\NewslettersRepository;
 use MailPoet\Newsletter\Sending\SendingQueuesRepository;
@@ -75,4 +77,23 @@ class NewslettersResponseBuilderTest extends \MailPoetTest {
     $response = $responseBuilder->buildForListing([$newsletter]);
     verify($response[0]['subject'])->equals('Hello [mailpoet/subscriber-firstname default="subscriber"]!');
   }
+
+  public function testItReplacesPersonalizationTagsInSentEmail() {
+    $em = $this->diContainer->get(EntityManager::class);
+    $responseBuilder = $this->diContainer->get(NewslettersResponseBuilder::class);
+    $em->persist($newsletter = new NewsletterEntity);
+    $newsletter->setType(NewsletterEntity::TYPE_STANDARD);
+    $newsletter->setStatus(NewsletterEntity::STATUS_SENT);
+    $newsletter->setSubject('Subject');
+    $em->persist($task = new ScheduledTaskEntity());
+    $em->persist($queue = new SendingQueueEntity());
+    $queue->setNewsletter($newsletter);
+    $queue->setTask($task);
+    $queue->setNewsletterRenderedSubject('Hello <!--[mailpoet/subscriber-firstname default="subscriber"]-->!');
+    $em->flush();
+    $response = $responseBuilder->buildForListing([$newsletter]);
+    /** @var string[] $renderedQueue */
+    $renderedQueue = $response[0]['queue'];
+    verify($renderedQueue['newsletter_rendered_subject'])->equals('Hello [mailpoet/subscriber-firstname default="subscriber"]!');
+  }
 }