diff --git a/src/Symfony/Component/Messenger/CHANGELOG.md b/src/Symfony/Component/Messenger/CHANGELOG.md
index 6df7ddcd1f..f5a51a3468 100644
--- a/src/Symfony/Component/Messenger/CHANGELOG.md
+++ b/src/Symfony/Component/Messenger/CHANGELOG.md
@@ -7,6 +7,7 @@ CHANGELOG
  * Deprecated passing a `ContainerInterface` instance as first argument of the `ConsumeMessagesCommand` constructor,
    pass a `RoutableMessageBus`  instance instead.
  * Added support for auto trimming of Redis streams.
+ * `InMemoryTransport` handle acknowledged and rejected messages.
 
 4.3.0
 -----
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/InMemoryTransportTest.php b/src/Symfony/Component/Messenger/Tests/Transport/InMemoryTransportTest.php
index 2d37e624d3..22149f8a39 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/InMemoryTransportTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/InMemoryTransportTest.php
@@ -34,7 +34,20 @@ class InMemoryTransportTest extends TestCase
     {
         $envelope = new Envelope(new \stdClass());
         $this->transport->send($envelope);
-        $this->assertSame([$envelope], $this->transport->get());
+        $this->assertSame([$envelope], $this->transport->getSent());
+    }
+
+    public function testQueue()
+    {
+        $envelope1 = new Envelope(new \stdClass());
+        $this->transport->send($envelope1);
+        $envelope2 = new Envelope(new \stdClass());
+        $this->transport->send($envelope2);
+        $this->assertSame([$envelope1, $envelope2], $this->transport->get());
+        $this->transport->ack($envelope1);
+        $this->assertSame([$envelope2], $this->transport->get());
+        $this->transport->reject($envelope2);
+        $this->assertSame([], $this->transport->get());
     }
 
     public function testAck()
@@ -63,5 +76,6 @@ class InMemoryTransportTest extends TestCase
         $this->assertEmpty($this->transport->get(), 'Should be empty after reset');
         $this->assertEmpty($this->transport->getAcknowledged(), 'Should be empty after reset');
         $this->assertEmpty($this->transport->getRejected(), 'Should be empty after reset');
+        $this->assertEmpty($this->transport->getSent(), 'Should be empty after reset');
     }
 }
diff --git a/src/Symfony/Component/Messenger/Transport/InMemoryTransport.php b/src/Symfony/Component/Messenger/Transport/InMemoryTransport.php
index 1f458b68da..354bb601a1 100644
--- a/src/Symfony/Component/Messenger/Transport/InMemoryTransport.php
+++ b/src/Symfony/Component/Messenger/Transport/InMemoryTransport.php
@@ -36,12 +36,17 @@ class InMemoryTransport implements TransportInterface, ResetInterface
      */
     private $rejected = [];
 
+    /**
+     * @var Envelope[]
+     */
+    private $queue = [];
+
     /**
      * {@inheritdoc}
      */
     public function get(): iterable
     {
-        return $this->sent;
+        return array_values($this->queue);
     }
 
     /**
@@ -50,6 +55,8 @@ class InMemoryTransport implements TransportInterface, ResetInterface
     public function ack(Envelope $envelope): void
     {
         $this->acknowledged[] = $envelope;
+        $id = spl_object_hash($envelope);
+        unset($this->queue[$id]);
     }
 
     /**
@@ -58,6 +65,8 @@ class InMemoryTransport implements TransportInterface, ResetInterface
     public function reject(Envelope $envelope): void
     {
         $this->rejected[] = $envelope;
+        $id = spl_object_hash($envelope);
+        unset($this->queue[$id]);
     }
 
     /**
@@ -66,13 +75,15 @@ class InMemoryTransport implements TransportInterface, ResetInterface
     public function send(Envelope $envelope): Envelope
     {
         $this->sent[] = $envelope;
+        $id = spl_object_hash($envelope);
+        $this->queue[$id] = $envelope;
 
         return $envelope;
     }
 
     public function reset()
     {
-        $this->sent = $this->rejected = $this->acknowledged = [];
+        $this->sent = $this->queue = $this->rejected = $this->acknowledged = [];
     }
 
     /**
@@ -90,4 +101,12 @@ class InMemoryTransport implements TransportInterface, ResetInterface
     {
         return $this->rejected;
     }
+
+    /**
+     * @return Envelope[]
+     */
+    public function getSent(): array
+    {
+        return $this->sent;
+    }
 }