diff --git a/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php b/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php
index 10d46ca846b4e..e50db434ffc0c 100644
--- a/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php
+++ b/src/Symfony/Component/Mailer/Tests/Transport/TransportsTest.php
@@ -64,4 +64,28 @@ public function testTransportDoesNotExist()
         $this->expectExceptionMessage('The "foobar" transport does not exist (available transports: "foo", "bar").');
         $transport->send($email);
     }
+
+    public function testTransportRestoredAfterFailure()
+    {
+        $exception = new \Exception();
+
+        $fooTransport = $this->createMock(TransportInterface::class);
+        $fooTransport->method('send')
+            ->willThrowException($exception);
+
+        $transport = new Transports([
+            'foo' => $fooTransport,
+        ]);
+
+        $headers = (new Headers())->addTextHeader('X-Transport', 'foo');
+        $email = new Message($headers, new TextPart('...'));
+
+        $this->expectExceptionObject($exception);
+
+        try {
+            $transport->send($email);
+        } finally {
+            $this->assertSame('foo', $email->getHeaders()->getHeaderBody('X-Transport'));
+        }
+    }
 }
diff --git a/src/Symfony/Component/Mailer/Transport/Transports.php b/src/Symfony/Component/Mailer/Transport/Transports.php
index c8f7970b32ef5..702fc5c784cd4 100644
--- a/src/Symfony/Component/Mailer/Transport/Transports.php
+++ b/src/Symfony/Component/Mailer/Transport/Transports.php
@@ -59,7 +59,13 @@ public function send(RawMessage $message, Envelope $envelope = null): ?SentMessa
             throw new InvalidArgumentException(sprintf('The "%s" transport does not exist (available transports: "%s").', $transport, implode('", "', array_keys($this->transports))));
         }
 
-        return $this->transports[$transport]->send($message, $envelope);
+        try {
+            return $this->transports[$transport]->send($message, $envelope);
+        } catch (\Throwable $e) {
+            $headers->addTextHeader('X-Transport', $transport);
+
+            throw $e;
+        }
     }
 
     public function __toString(): string