diff --git a/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml b/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml
index b4e6cd69ef64a..55976d1c02269 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml
+++ b/src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.xml
@@ -67,6 +67,10 @@
             <argument type="service" id="messenger.transport.serializer" />
         </service>
 
+        <service id="messenger.transport.sync.factory" class="Symfony\Component\Messenger\Transport\Sync\SyncTransportFactory">
+            <tag name="messenger.transport_factory" />
+        </service>
+
         <!-- retry -->
         <service id="messenger.retry_strategy_locator">
             <tag name="container.service_locator" />
diff --git a/src/Symfony/Component/Messenger/CHANGELOG.md b/src/Symfony/Component/Messenger/CHANGELOG.md
index 9638de4e49092..41a7e3438e0d9 100644
--- a/src/Symfony/Component/Messenger/CHANGELOG.md
+++ b/src/Symfony/Component/Messenger/CHANGELOG.md
@@ -4,6 +4,8 @@ CHANGELOG
 4.3.0
 -----
 
+ * Added a new `SyncTransport` along with `ForceCallHandlersStamp` to
+   explicitly handle messages asynchronously.
  * Added optional parameter `prefetch_count` in connection configuration, 
    to setup channel prefetch count
  * New classes: `RoutableMessageBus`, `AddBusNameStampMiddleware`
diff --git a/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php b/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php
index f1b561d03a18d..d2ebaf8cfa011 100644
--- a/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php
+++ b/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php
@@ -15,6 +15,7 @@
 use Psr\Log\NullLogger;
 use Symfony\Component\Messenger\Envelope;
 use Symfony\Component\Messenger\Event\SendMessageToTransportsEvent;
+use Symfony\Component\Messenger\Stamp\ForceCallHandlersStamp;
 use Symfony\Component\Messenger\Stamp\ReceivedStamp;
 use Symfony\Component\Messenger\Stamp\RedeliveryStamp;
 use Symfony\Component\Messenger\Stamp\SentStamp;
@@ -81,7 +82,13 @@ public function handle(Envelope $envelope, StackInterface $stack): Envelope
                     $envelope = $sender->send($envelope->with(new SentStamp(\get_class($sender), \is_string($alias) ? $alias : null)));
                 }
 
-                // on a redelivery, never call local handlers
+                // if the message was marked (usually by SyncTransport) that it handlers
+                // MUST be called, mark them to be handled.
+                if (null !== $envelope->last(ForceCallHandlersStamp::class)) {
+                    $handle = true;
+                }
+
+                // on a redelivery, only send back to queue: never call local handlers
                 if (null !== $redeliveryStamp) {
                     $handle = false;
                 }
diff --git a/src/Symfony/Component/Messenger/Stamp/ForceCallHandlersStamp.php b/src/Symfony/Component/Messenger/Stamp/ForceCallHandlersStamp.php
new file mode 100644
index 0000000000000..5c9eb3a6d96dd
--- /dev/null
+++ b/src/Symfony/Component/Messenger/Stamp/ForceCallHandlersStamp.php
@@ -0,0 +1,27 @@
+<?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\Stamp;
+
+/**
+ * Stamp marks that the handlers *should* be called immediately.
+ *
+ * This is used by the SyncTransport to indicate to the
+ * SendMessageMiddleware that handlers *should* be called
+ * immediately, even though a transport was set.
+ *
+ * @experimental in 4.3
+ *
+ * @author Ryan Weaver <ryan@symfonycasts.com>
+ */
+class ForceCallHandlersStamp implements StampInterface
+{
+}
diff --git a/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php b/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php
index 301f01b86086b..92e48bc78204d 100644
--- a/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Middleware/SendMessageMiddlewareTest.php
@@ -14,6 +14,7 @@
 use Symfony\Component\Messenger\Envelope;
 use Symfony\Component\Messenger\Event\SendMessageToTransportsEvent;
 use Symfony\Component\Messenger\Middleware\SendMessageMiddleware;
+use Symfony\Component\Messenger\Stamp\ForceCallHandlersStamp;
 use Symfony\Component\Messenger\Stamp\ReceivedStamp;
 use Symfony\Component\Messenger\Stamp\RedeliveryStamp;
 use Symfony\Component\Messenger\Stamp\SentStamp;
@@ -86,6 +87,8 @@ public function testItSendsTheMessageToMultipleSenders()
     public function testItSendsToOnlyOneSenderOnRedelivery()
     {
         $envelope = new Envelope(new DummyMessage('Hey'), new RedeliveryStamp(5, 'bar'));
+        // even with a ForceCallHandlersStamp, the next middleware won't be called
+        $envelope = $envelope->with(new ForceCallHandlersStamp());
         $sender = $this->getMockBuilder(SenderInterface::class)->getMock();
         $sender2 = $this->getMockBuilder(SenderInterface::class)->getMock();
 
@@ -237,7 +240,7 @@ public function testItDoesNotDispatchWithNoSenders()
         $middleware->handle($envelope, $this->getStackMock());
     }
 
-    public function testItDoesNotDispatchOnRetry()
+    public function testItDoesNotDispatchOnRedeliver()
     {
         $envelope = new Envelope(new DummyMessage('original envelope'));
         $envelope = $envelope->with(new RedeliveryStamp(3, 'foo_sender'));
@@ -251,4 +254,18 @@ public function testItDoesNotDispatchOnRetry()
 
         $middleware->handle($envelope, $this->getStackMock(false));
     }
+
+    public function testItHandlesWithForceCallHandlersStamp()
+    {
+        $envelope = new Envelope(new DummyMessage('original envelope'));
+        $envelope = $envelope->with(new ForceCallHandlersStamp());
+
+        $sender = $this->getMockBuilder(SenderInterface::class)->getMock();
+        $sender->expects($this->once())->method('send')->willReturn($envelope);
+
+        $middleware = new SendMessageMiddleware(new SendersLocator([DummyMessage::class => [$sender]]));
+
+        // next handler *should* be called
+        $middleware->handle($envelope, $this->getStackMock(true));
+    }
 }
diff --git a/src/Symfony/Component/Messenger/Transport/Sync/SyncTransport.php b/src/Symfony/Component/Messenger/Transport/Sync/SyncTransport.php
new file mode 100644
index 0000000000000..6d45e7f6df34c
--- /dev/null
+++ b/src/Symfony/Component/Messenger/Transport/Sync/SyncTransport.php
@@ -0,0 +1,52 @@
+<?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\Sync;
+
+use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Exception\InvalidArgumentException;
+use Symfony\Component\Messenger\Stamp\ForceCallHandlersStamp;
+use Symfony\Component\Messenger\Transport\TransportInterface;
+
+/**
+ * A "fake" transport that marks messages to be handled immediately.
+ *
+ * @experimental in 4.3
+ *
+ * @author Ryan Weaver <ryan@symfonycasts.com>
+ */
+class SyncTransport implements TransportInterface
+{
+    public function receive(callable $handler): void
+    {
+        throw new InvalidArgumentException('You cannot receive messages from the SyncTransport.');
+    }
+
+    public function stop(): void
+    {
+        throw new InvalidArgumentException('You cannot call stop() on the SyncTransport.');
+    }
+
+    public function ack(Envelope $envelope): void
+    {
+        throw new InvalidArgumentException('You cannot call ack() on the SyncTransport.');
+    }
+
+    public function reject(Envelope $envelope): void
+    {
+        throw new InvalidArgumentException('You cannot call reject() on the SyncTransport.');
+    }
+
+    public function send(Envelope $envelope): Envelope
+    {
+        return $envelope->with(new ForceCallHandlersStamp());
+    }
+}
diff --git a/src/Symfony/Component/Messenger/Transport/Sync/SyncTransportFactory.php b/src/Symfony/Component/Messenger/Transport/Sync/SyncTransportFactory.php
new file mode 100644
index 0000000000000..0eba740813a56
--- /dev/null
+++ b/src/Symfony/Component/Messenger/Transport/Sync/SyncTransportFactory.php
@@ -0,0 +1,33 @@
+<?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\Sync;
+
+use Symfony\Component\Messenger\Transport\TransportFactoryInterface;
+use Symfony\Component\Messenger\Transport\TransportInterface;
+
+/**
+ * @experimental in 4.3
+ *
+ * @author Ryan Weaver <ryan@symfonycasts.com>
+ */
+class SyncTransportFactory implements TransportFactoryInterface
+{
+    public function createTransport(string $dsn, array $options): TransportInterface
+    {
+        return new SyncTransport();
+    }
+
+    public function supports(string $dsn, array $options): bool
+    {
+        return 0 === strpos($dsn, 'sync://');
+    }
+}