diff --git a/src/Symfony/Component/Mailer/Bridge/Mailjet/Tests/Transport/MailjetApiTransportTest.php b/src/Symfony/Component/Mailer/Bridge/Mailjet/Tests/Transport/MailjetApiTransportTest.php
index 703b01dc34e31..21510febce4f1 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailjet/Tests/Transport/MailjetApiTransportTest.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailjet/Tests/Transport/MailjetApiTransportTest.php
@@ -102,15 +102,21 @@ public function testSendSuccess()
     {
         $json = json_encode([
             'Messages' => [
-                'foo' => 'bar',
+                [
+                    'Status' => 'success',
+                    'To' => [
+                        [
+                            'Email' => 'passenger1@mailjet.com',
+                            'MessageUUID' => '7c5f9f29-42ba-4959-b19c-dcd8b2f327ca',
+                            'MessageID' => '576460756513665525',
+                            'MessageHref' => 'https://api.mailjet.com/v3/message/576460756513665525',
+                        ],
+                    ],
+                ],
             ],
         ]);
 
-        $responseHeaders = [
-            'x-mj-request-guid' => ['baz'],
-        ];
-
-        $response = new MockResponse($json, ['response_headers' => $responseHeaders]);
+        $response = new MockResponse($json);
 
         $client = new MockHttpClient($response);
 
@@ -124,7 +130,7 @@ public function testSendSuccess()
 
         $sentMessage = $transport->send($email);
         $this->assertInstanceOf(SentMessage::class, $sentMessage);
-        $this->assertSame('baz', $sentMessage->getMessageId());
+        $this->assertSame('576460756513665525', $sentMessage->getMessageId());
     }
 
     public function testSendWithDecodingException()
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailjet/Transport/MailjetApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailjet/Transport/MailjetApiTransport.php
index 8440ecf9ab3f3..d3803ccf54dbb 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailjet/Transport/MailjetApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailjet/Transport/MailjetApiTransport.php
@@ -85,7 +85,7 @@ protected function doSendApi(SentMessage $sentMessage, Email $email, Envelope $e
             throw new HttpTransportException(sprintf('Unable to send an email: "%s" malformed api response.', $response->getContent(false)), $response);
         }
 
-        $sentMessage->setMessageId($response->getHeaders(false)['x-mj-request-guid'][0]);
+        $sentMessage->setMessageId($result['Messages'][0]['To'][0]['MessageID'] ?? '');
 
         return $response;
     }