title: swiftmailer configuration for more than one accounts in Symfony 2
body: <p>I use gmail to send mails ,so I config ‘config.yml’ like this</p>
  
  <pre><code>swiftmailer:
  transport: %mailer_transport%
  encryption: %mailer_encryption%
  auth_mode: %mailer_auth%
  host:      %mailer_host%
  username:  %mailer_user%
  password:  %mailer_password%
  </code></pre>
  
  <p>‘parameters.yml’ like this</p>
  
  <pre><code>mailer_transport:  smtp
  mailer_encryption: ssl
  mailer_auth:       login
  mailer_host:       smtp.gmail.com
  mailer_user:       lee@gmail.com
  mailer_password:   ******
  </code></pre>
  
  <p>Now I want to use more mail accounts to send mails for different goals.
  eg:Use lee@gmail.com send mails for welcome;Use lee1@gmail.com send mails for reset password.</p>
  
  <p>What should I config swiftmailer？</p>