Allowed array of emails for "to_email" parameter.

Author: phansys

DependencyInjection/Configuration.php

@@ -92,7 +92,13 @@ public function getConfigTreeBuilder()
                                 ->prototype('scalar')->end()
                             ->end()
                             ->scalarNode('from_email')->end() // swift_mailer and native_mailer
-                            ->scalarNode('to_email')->end() // swift_mailer and native_mailer
+                            ->arrayNode('to_email') // swift_mailer and native_mailer
+                                ->prototype('scalar')->end()
+                                ->beforeNormalization()
+                                    ->ifString()
+                                    ->then(function($v) { return array('id' => $v); })
+                                ->end()
+                            ->end()
                             ->scalarNode('subject')->end() // swift_mailer and native_mailer
                             ->arrayNode('email_prototype') // swift_mailer
                                 ->canBeUnset()