VPS上的邮件排队和传递失败

我通过软件与cpanel和IM买了一个新的VPS与我的电子邮件有几个问题

当我发送电子邮件给任何使用Gmail,雅虎,Hotmail的人,它会排队,并在大约72小时后返回与交付失败

This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: [email protected] retry timeout exceeded 

即时通讯使用cPanel邮件和im使用softlayer的默认名称服务器

 ns1.softlayer.com ns2.softlayer.com 

和即时我的MXlogging,我有

 mail.mydoamin.com 

有人能告诉我什么一定是错的?