在web.config中设置多个SMTP设置？

<configuration>
  <system.net>
    <mailSettings>
      <smtp from="sender@example.com">
        <network host="smtp1.example.com" port="25" userName="username1" password="password1" />
      </smtp>
      <smtp from="sender@example.com">
        <network host="smtp2.example.com" port="25" userName="username2" password="password2" />
      </smtp>
    </mailSettings>
  </system.net>
</configuration>