关于发送邮件的 553 this mail is blocked by kbas system 错误。
使用自己写的程序，通过一个公司的邮箱发送没有问题，通过163，tom的免费邮箱，   发送在认证通过以后，发送DATA确认以后得到
“553   this   mail   is   blocked   by   kbas   system”，   这个是什么原因阿。
同时使用相同的tom的帐号，使用foxmail发送就可以，不是是什么原因。

------解决方案--------------------
看上去你的邮件被当作了垃圾邮件了。

摘自某篇报道：

The KBAS system developed by Shenzhen-based Hanqi Technology is reportedly a better anti-spam software solution than many hardware-based systems. The system is suitable for various operation systems and hardware environment, and it is reliable and efficient. In particular, it makes a great breakthrough in filtering Chinese-language spam.

One of the main reasons for Tom.com to choose KBAS is reportedly because of its powerful filtering function. When KBAS is installed separately in a dozen outbound UNIX servers, the email sent out will be first filtered by KBAS and only non-spam emails will ultimately be sent out. Statistics show that the daily emails sent before and after KBAS is installed is more than 50 million and several million, respectively. This means that KBAS will filter more than 40 million spam each day on high performace systems like those used by Tom.com.

另外这个帖子也可参考一下：
http://www.delphibbs.com/delphibbs/dispq.asp?lid=3359545