diff --git a/src/Symfony/Bundle/FrameworkBundle/Test/MailerAssertionsTrait.php b/src/Symfony/Bundle/FrameworkBundle/Test/MailerAssertionsTrait.php
index 4b1c0388e8..c709fea0f2 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Test/MailerAssertionsTrait.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Test/MailerAssertionsTrait.php
@@ -25,6 +25,11 @@ trait MailerAssertionsTrait
         self::assertThat(self::getMessageMailerEvents(), new MailerConstraint\EmailCount($count, $transport), $message);
     }
 
+    public static function assertQueuedEmailCount(int $count, string $transport = null, string $message = ''): void
+    {
+        self::assertThat(self::getMessageMailerEvents(), new MailerConstraint\EmailCount($count, $transport, true), $message);
+    }
+
     public static function assertEmailIsQueued(MessageEvent $event, string $message = ''): void
     {
         self::assertThat($event, new MailerConstraint\EmailIsQueued(), $message);
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/MailerTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/MailerTest.php
index 0812c6254b..da5390950f 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/MailerTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/MailerTest.php
@@ -3,6 +3,7 @@
 namespace Symfony\Bundle\FrameworkBundle\Tests\Functional;
 
 use Psr\Log\LoggerInterface;
+use Symfony\Bundle\FullStack;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\Mailer\Mailer;
 use Symfony\Component\Mailer\SentMessage;
@@ -71,9 +72,19 @@ class MailerTest extends AbstractWebTestCase
         $client->request('GET', '/send_email');
 
         $this->assertEmailCount(2);
-        $this->assertEmailIsQueued($this->getMailerEvent(0));
+        $first = 0;
+        $second = 1;
+        if (!class_exists(FullStack::class)) {
+            $this->assertQueuedEmailCount(2);
+            $first = 1;
+            $second = 3;
+            $this->assertEmailIsQueued($this->getMailerEvent(0));
+            $this->assertEmailIsQueued($this->getMailerEvent(2));
+        }
+        $this->assertEmailIsNotQueued($this->getMailerEvent($first));
+        $this->assertEmailIsNotQueued($this->getMailerEvent($second));
 
-        $email = $this->getMailerMessage(0);
+        $email = $this->getMailerMessage($first);
         $this->assertEmailHasHeader($email, 'To');
         $this->assertEmailHeaderSame($email, 'To', 'fabien@symfony.com');
         $this->assertEmailHeaderNotSame($email, 'To', 'helene@symfony.com');
@@ -83,7 +94,7 @@ class MailerTest extends AbstractWebTestCase
         $this->assertEmailHtmlBodyNotContains($email, 'Bar');
         $this->assertEmailAttachementCount($email, 1);
 
-        $email = $this->getMailerMessage(1);
+        $email = $this->getMailerMessage($second);
         $this->assertEmailAddressContains($email, 'To', 'fabien@symfony.com');
         $this->assertEmailAddressContains($email, 'To', 'thomas@symfony.com');
         $this->assertEmailAddressContains($email, 'Reply-To', 'me@symfony.com');
diff --git a/src/Symfony/Component/Mailer/Mailer.php b/src/Symfony/Component/Mailer/Mailer.php
index 935607793e..b00ab4da0c 100644
--- a/src/Symfony/Component/Mailer/Mailer.php
+++ b/src/Symfony/Component/Mailer/Mailer.php
@@ -54,7 +54,7 @@ class Mailer implements MailerInterface
                     throw new TransportException('Cannot send message without a valid envelope.', 0, $e);
                 }
             }
-            $event = new MessageEvent($message, $envelope, $this->transport->getName());
+            $event = new MessageEvent($message, $envelope, $this->transport->getName(), true);
             $this->dispatcher->dispatch($event);
         }
 
diff --git a/src/Symfony/Component/Mailer/Test/Constraint/EmailCount.php b/src/Symfony/Component/Mailer/Test/Constraint/EmailCount.php
index 563c04b3af..59a78123db 100644
--- a/src/Symfony/Component/Mailer/Test/Constraint/EmailCount.php
+++ b/src/Symfony/Component/Mailer/Test/Constraint/EmailCount.php
@@ -18,11 +18,13 @@ final class EmailCount extends Constraint
 {
     private $expectedValue;
     private $transport;
+    private $queued;
 
-    public function __construct(int $expectedValue, string $transport = null)
+    public function __construct(int $expectedValue, string $transport = null, bool $queued = false)
     {
         $this->expectedValue = $expectedValue;
         $this->transport = $transport;
+        $this->queued = $queued;
     }
 
     /**
@@ -30,7 +32,7 @@ final class EmailCount extends Constraint
      */
     public function toString(): string
     {
-        return sprintf('%shas sent "%d" emails', $this->transport ? $this->transport.' ' : '', $this->expectedValue);
+        return sprintf('%shas %s "%d" emails', $this->transport ? $this->transport.' ' : '', $this->queued ? 'queued' : 'sent', $this->expectedValue);
     }
 
     /**
@@ -40,7 +42,7 @@ final class EmailCount extends Constraint
      */
     protected function matches($events): bool
     {
-        return $this->expectedValue === \count($events->getEvents($this->transport));
+        return $this->expectedValue === $this->countEmails($events);
     }
 
     /**
@@ -50,6 +52,22 @@ final class EmailCount extends Constraint
      */
     protected function failureDescription($events): string
     {
-        return sprintf('the Transport %s (%d sent)', $this->toString(), \count($events->getEvents($this->transport)));
+        return sprintf('the Transport %s (%d %s)', $this->toString(), $this->countEmails($events), $this->queued ? 'queued' : 'sent');
+    }
+
+    private function countEmails(MessageEvents $events): int
+    {
+        $count = 0;
+        foreach ($events->getEvents($this->transport) as $event) {
+            if (
+                ($this->queued && $event->isQueued())
+                ||
+                (!$this->queued && !$event->isQueued())
+            ) {
+                ++$count;
+            }
+        }
+
+        return $count;
     }
 }
diff --git a/src/Symfony/Component/Mailer/Transport/AbstractTransport.php b/src/Symfony/Component/Mailer/Transport/AbstractTransport.php
index a50e3c9b34..018b4612e9 100644
--- a/src/Symfony/Component/Mailer/Transport/AbstractTransport.php
+++ b/src/Symfony/Component/Mailer/Transport/AbstractTransport.php
@@ -67,7 +67,7 @@ abstract class AbstractTransport implements TransportInterface
             }
         }
 
-        $event = new MessageEvent($message, $envelope, $this->getName(), true);
+        $event = new MessageEvent($message, $envelope, $this->getName());
         $this->dispatcher->dispatch($event);
         $envelope = $event->getEnvelope();
         if (!$envelope->getRecipients()) {