当使用sp_send_dbmail时，出现错误：邮件服务器失败，请求的名称有效，但没有找到所请求类型的数据）

Question

当我使用此代码时尝试从sql server发送电子邮件

exec msdb.dbo.sp_send_dbmail 
        @recipients='yang.liu@hotmail.com',
        @body= 'abc', 
        @subject = 'new request',
        @profile_name ='thisProfile'

sql server management show me：邮件排队。

但实际上，当我查看日志以查看原因时，此电子邮件尚未发送：

SELECT TOP 100 [log_id]
      ,[event_type]
      ,[log_date]
      ,[description]
      ,[process_id]
      ,[mailitem_id]
      ,[account_id]
      ,[last_mod_date]
      ,[last_mod_user]
  FROM [msdb].[dbo].[sysmail_event_log]

  order by [log_id] desc

日志告诉我：

The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 1 (2014-07-10T10:34:17). Exception Message: Could not connect to mail server. (The requested name is valid, but no data of the requested type was found).

任何人都可以告诉我是什么原因，谢谢