'components' => [
 'db' => [
  'class' => 'yii\db\Connection',
  'dsn' => 'mysql:host=localhost;dbname=yiidemo',
  'username' => 'root',
  'password' => 'root',
  'charset' => 'utf8',
 ],
 'mailer' => [
  'class' => 'yii\swiftmailer\Mailer',
  'viewPath' => '@common/mail',
  // send all mails to a file by default. You have to set
  // 'useFileTransport' to false and configure a transport
  // for the mailer to send real emails.
  'useFileTransport' => true,
  'transport' => [ 
   'class' => 'Swift_SmtpTransport', 
   'host' => 'smtp.qq.com', 
   'username' => '********@qq.com', 
   'password' => '********',
   'port' => '465', 
   'encryption' => 'ssl', 
  ], 
 ],
],