Allow skipping mail sending if a listener to MessageSending returned false

Author: themsaid

src/Illuminate/Mail/Mailer.php

@@ -428,8 +428,8 @@ protected function createMessage()
      */
     protected function sendSwiftMessage($message)
     {
-        if ($this->events) {
-            $this->events->dispatch(new Events\MessageSending($message));
+        if (! $this->shouldSendMessage($message)) {
+            return;
         }
 
         try {
@@ -439,6 +439,23 @@ protected function sendSwiftMessage($message)
         }
     }
 
+    /**
+     * Determines if the message can be sent.
+     *
+     * @param  \Swift_Message  $message
+     * @return bool
+     */
+    protected function shouldSendMessage($message)
+    {
+        if (! $this->events) {
+            return true;
+        }
+
+        return $this->events->until(
+            new Events\MessageSending($message)
+        ) !== false;
+    }
+
     /**
      * Force the transport to re-connect.
      *