diff --git a/src/Symfony/Component/Messenger/Stamp/SentToFailureTransportStamp.php b/src/Symfony/Component/Messenger/Stamp/SentToFailureTransportStamp.php
index 05a5dfcacf77b..222aa6a18dd6b 100644
--- a/src/Symfony/Component/Messenger/Stamp/SentToFailureTransportStamp.php
+++ b/src/Symfony/Component/Messenger/Stamp/SentToFailureTransportStamp.php
@@ -32,7 +32,7 @@ public function __construct(string $exceptionMessage, string $originalReceiverNa
         $this->exceptionMessage = $exceptionMessage;
         $this->originalReceiverName = $originalReceiverName;
         $this->flattenException = $flattenException;
-        $this->sentAt = new \DateTime();
+        $this->sentAt = new \DateTimeImmutable();
     }
 
     public function getExceptionMessage(): string
@@ -50,7 +50,7 @@ public function getFlattenException(): ?FlattenException
         return $this->flattenException;
     }
 
-    public function getSentAt(): \DateTime
+    public function getSentAt(): \DateTimeInterface
     {
         return $this->sentAt;
     }
diff --git a/src/Symfony/Component/Messenger/Tests/Stamp/SentToFailureTransportStampTest.php b/src/Symfony/Component/Messenger/Tests/Stamp/SentToFailureTransportStampTest.php
index 7639060daa178..3b9579a6460ee 100644
--- a/src/Symfony/Component/Messenger/Tests/Stamp/SentToFailureTransportStampTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Stamp/SentToFailureTransportStampTest.php
@@ -28,6 +28,6 @@ public function testGetters()
         $this->assertSame('exception message', $stamp->getExceptionMessage());
         $this->assertSame('original_receiver', $stamp->getOriginalReceiverName());
         $this->assertSame($flattenException, $stamp->getFlattenException());
-        $this->assertInstanceOf(\DateTime::class, $stamp->getSentAt());
+        $this->assertInstanceOf(\DateTimeInterface::class, $stamp->getSentAt());
     }
 }
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php
index 79c99d5be3410..3a250fddbc4ec 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineReceiverTest.php
@@ -36,7 +36,7 @@ public function testItReturnsTheDecodedMessageToTheHandler()
         $connection->method('get')->willReturn($doctrineEnvelope);
 
         $receiver = new DoctrineReceiver($connection, $serializer);
-        $actualEnvelopes = iterator_to_array($receiver->get());
+        $actualEnvelopes = $receiver->get();
         $this->assertCount(1, $actualEnvelopes);
         /** @var Envelope $actualEnvelope */
         $actualEnvelope = $actualEnvelopes[0];
@@ -67,7 +67,7 @@ public function testItRejectTheMessageIfThereIsAMessageDecodingFailedException()
         $connection->expects($this->once())->method('reject');
 
         $receiver = new DoctrineReceiver($connection, $serializer);
-        iterator_to_array($receiver->get());
+        $receiver->get();
     }
 
     public function testAll()
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php
index 145397f889a04..ad9f9dba613d2 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineTransportTest.php
@@ -46,7 +46,7 @@ public function testReceivesMessages()
         $serializer->method('decode')->with(['body' => 'body', 'headers' => ['my' => 'header']])->willReturn(new Envelope($decodedMessage));
         $connection->method('get')->willReturn($doctrineEnvelope);
 
-        $envelopes = iterator_to_array($transport->get());
+        $envelopes = $transport->get();
         $this->assertSame($decodedMessage, $envelopes[0]->getMessage());
     }
 
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Receiver/SingleMessageReceiverTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Receiver/SingleMessageReceiverTest.php
index a900e7ba0ff55..e8f5ef4ce1720 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Receiver/SingleMessageReceiverTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Receiver/SingleMessageReceiverTest.php
@@ -13,12 +13,8 @@
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Messenger\Envelope;
-use Symfony\Component\Messenger\Tests\Fixtures\DummyMessage;
-use Symfony\Component\Messenger\Tests\Fixtures\SecondMessage;
 use Symfony\Component\Messenger\Transport\Receiver\ReceiverInterface;
 use Symfony\Component\Messenger\Transport\Receiver\SingleMessageReceiver;
-use Symfony\Component\Messenger\Transport\Sender\SenderInterface;
-use Symfony\Component\Messenger\Transport\Sender\SendersLocator;
 
 class SingleMessageReceiverTest extends TestCase
 {
@@ -28,11 +24,11 @@ public function testItReceivesOnlyOneMessage()
         $envelope = new Envelope(new \stdClass());
 
         $receiver = new SingleMessageReceiver($innerReceiver, $envelope);
-        $received = \iterator_to_array($receiver->get());
+        $received = $receiver->get();
         $this->assertCount(1, $received);
         $this->assertSame($received[0], $envelope);
 
-        $this->assertEmpty(\iterator_to_array($receiver->get()));
+        $this->assertEmpty($receiver->get());
     }
 
     public function testCallsAreForwarded()
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php
index c3bb532239756..28c299258ca49 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisReceiverTest.php
@@ -33,7 +33,7 @@ public function testItReturnsTheDecodedMessageToTheHandler()
         $connection->method('get')->willReturn($redisEnvelop);
 
         $receiver = new RedisReceiver($connection, $serializer);
-        $actualEnvelopes = iterator_to_array($receiver->get());
+        $actualEnvelopes = $receiver->get();
         $this->assertCount(1, $actualEnvelopes);
         $this->assertEquals(new DummyMessage('Hi'), $actualEnvelopes[0]->getMessage());
     }
@@ -51,7 +51,7 @@ public function testItRejectTheMessageIfThereIsAMessageDecodingFailedException()
         $connection->expects($this->once())->method('reject');
 
         $receiver = new RedisReceiver($connection, $serializer);
-        iterator_to_array($receiver->get());
+        $receiver->get();
     }
 
     private function createRedisEnvelope()
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php
index 0c83e6be88c46..fce73e50d3cdc 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/RedisTransportTest.php
@@ -46,7 +46,7 @@ public function testReceivesMessages()
         $serializer->method('decode')->with(['body' => 'body', 'headers' => ['my' => 'header']])->willReturn(new Envelope($decodedMessage));
         $connection->method('get')->willReturn($redisEnvelope);
 
-        $envelopes = iterator_to_array($transport->get());
+        $envelopes = $transport->get();
         $this->assertSame($decodedMessage, $envelopes[0]->getMessage());
     }
 
diff --git a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php
index d2d03c859cdeb..db2f1202f91ee 100644
--- a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php
+++ b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php
@@ -57,7 +57,7 @@ private function getEnvelope(string $queueName): iterable
         }
 
         if (null === $amqpEnvelope) {
-            return [];
+            return;
         }
 
         try {
diff --git a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php
index 91c9fe45c0c3a..242a1382304ee 100644
--- a/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php
+++ b/src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php
@@ -84,12 +84,12 @@ public function getMessageCount(): int
         return ($this->receiver ?? $this->getReceiver())->getMessageCount();
     }
 
-    private function getReceiver()
+    private function getReceiver(): AmqpReceiver
     {
         return $this->receiver = new AmqpReceiver($this->connection, $this->serializer);
     }
 
-    private function getSender()
+    private function getSender(): AmqpSender
     {
         return $this->sender = new AmqpSender($this->connection, $this->serializer);
     }
diff --git a/src/Symfony/Component/Messenger/Transport/Doctrine/DoctrineReceiver.php b/src/Symfony/Component/Messenger/Transport/Doctrine/DoctrineReceiver.php
index aad8cf236d5aa..a6a41e8c79f46 100644
--- a/src/Symfony/Component/Messenger/Transport/Doctrine/DoctrineReceiver.php
+++ b/src/Symfony/Component/Messenger/Transport/Doctrine/DoctrineReceiver.php
@@ -54,7 +54,7 @@ public function get(): iterable
             return [];
         }
 
-        yield $this->createEnvelopeFromData($doctrineEnvelope);
+        return [$this->createEnvelopeFromData($doctrineEnvelope)];
     }
 
     /**
diff --git a/src/Symfony/Component/Messenger/Transport/Receiver/ListableReceiverInterface.php b/src/Symfony/Component/Messenger/Transport/Receiver/ListableReceiverInterface.php
index b4c19295a9318..ff16a4d436375 100644
--- a/src/Symfony/Component/Messenger/Transport/Receiver/ListableReceiverInterface.php
+++ b/src/Symfony/Component/Messenger/Transport/Receiver/ListableReceiverInterface.php
@@ -1,5 +1,14 @@
 <?php
 
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
 namespace Symfony\Component\Messenger\Transport\Receiver;
 
 use Symfony\Component\Messenger\Envelope;
diff --git a/src/Symfony/Component/Messenger/Transport/Receiver/SingleMessageReceiver.php b/src/Symfony/Component/Messenger/Transport/Receiver/SingleMessageReceiver.php
index 9aec49d6c0af5..56a1399518e01 100644
--- a/src/Symfony/Component/Messenger/Transport/Receiver/SingleMessageReceiver.php
+++ b/src/Symfony/Component/Messenger/Transport/Receiver/SingleMessageReceiver.php
@@ -1,5 +1,14 @@
 <?php
 
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
 namespace Symfony\Component\Messenger\Transport\Receiver;
 
 use Symfony\Component\Messenger\Envelope;
@@ -32,7 +41,7 @@ public function get(): iterable
 
         $this->hasReceived = true;
 
-        yield $this->envelope;
+        return [$this->envelope];
     }
 
     public function ack(Envelope $envelope): void
diff --git a/src/Symfony/Component/Messenger/Transport/RedisExt/RedisReceiver.php b/src/Symfony/Component/Messenger/Transport/RedisExt/RedisReceiver.php
index 8ff60354b9415..fe18491f6da5d 100644
--- a/src/Symfony/Component/Messenger/Transport/RedisExt/RedisReceiver.php
+++ b/src/Symfony/Component/Messenger/Transport/RedisExt/RedisReceiver.php
@@ -57,7 +57,7 @@ public function get(): iterable
             throw $exception;
         }
 
-        yield $envelope->with(new RedisReceivedStamp($redisEnvelope['id']));
+        return [$envelope->with(new RedisReceivedStamp($redisEnvelope['id']))];
     }
 
     /**
diff --git a/src/Symfony/Component/Messenger/Transport/RedisExt/RedisTransport.php b/src/Symfony/Component/Messenger/Transport/RedisExt/RedisTransport.php
index 3af4e94233675..7ce75e71272b0 100644
--- a/src/Symfony/Component/Messenger/Transport/RedisExt/RedisTransport.php
+++ b/src/Symfony/Component/Messenger/Transport/RedisExt/RedisTransport.php
@@ -76,12 +76,12 @@ public function setup(): void
         $this->connection->setup();
     }
 
-    private function getReceiver()
+    private function getReceiver(): RedisReceiver
     {
         return $this->receiver = new RedisReceiver($this->connection, $this->serializer);
     }
 
-    private function getSender()
+    private function getSender(): RedisSender
     {
         return $this->sender = new RedisSender($this->connection, $this->serializer);
     }
diff --git a/src/Symfony/Component/Messenger/Worker.php b/src/Symfony/Component/Messenger/Worker.php
index 44ff30a7297c4..4018755ff633b 100644
--- a/src/Symfony/Component/Messenger/Worker.php
+++ b/src/Symfony/Component/Messenger/Worker.php
@@ -136,16 +136,11 @@ private function handleMessage(Envelope $envelope, ReceiverInterface $receiver,
                 $envelope = $throwable->getEnvelope();
             }
 
-            $shouldRetry = $this->shouldRetry($throwable, $envelope, $retryStrategy);
+            $shouldRetry = $retryStrategy && $this->shouldRetry($throwable, $envelope, $retryStrategy);
 
             $this->dispatchEvent(new WorkerMessageFailedEvent($envelope, $transportName, $throwable, $shouldRetry));
 
             if ($shouldRetry) {
-                if (null === $retryStrategy) {
-                    // not logically allowed, but check just in case
-                    throw new LogicException('Retrying is not supported without a retry strategy.');
-                }
-
                 $retryCount = $this->getRetryCount($envelope) + 1;
                 if (null !== $this->logger) {
                     $this->logger->error('Retrying {class} - retry #{retryCount}.', $context + ['retryCount' => $retryCount, 'error' => $throwable]);
@@ -194,16 +189,12 @@ private function dispatchEvent($event)
         $this->eventDispatcher->dispatch($event);
     }
 
-    private function shouldRetry(\Throwable $e, Envelope $envelope, ?RetryStrategyInterface $retryStrategy): bool
+    private function shouldRetry(\Throwable $e, Envelope $envelope, RetryStrategyInterface $retryStrategy): bool
     {
         if ($e instanceof UnrecoverableMessageHandlingException) {
             return false;
         }
 
-        if (null === $retryStrategy) {
-            return false;
-        }
-
         $sentStamp = $envelope->last(SentStamp::class);
         if (null === $sentStamp) {
             if (null !== $this->logger) {
diff --git a/src/Symfony/Component/Messenger/Worker/StopWhenRestartSignalIsReceived.php b/src/Symfony/Component/Messenger/Worker/StopWhenRestartSignalIsReceived.php
index 29b52c87da91b..1958d4ecc86a4 100644
--- a/src/Symfony/Component/Messenger/Worker/StopWhenRestartSignalIsReceived.php
+++ b/src/Symfony/Component/Messenger/Worker/StopWhenRestartSignalIsReceived.php
@@ -59,7 +59,7 @@ public function stop(): void
         $this->decoratedWorker->stop();
     }
 
-    private function shouldRestart(float $workerStartedAt)
+    private function shouldRestart(float $workerStartedAt): bool
     {
         $cacheItem = $this->cachePool->getItem(self::RESTART_REQUESTED_TIMESTAMP_KEY);