日志里显示is invalid or DNS says does not exist

bug52101

Mon 2007-08-27 13:39:46: --> 250-ETRN
Mon 2007-08-27 13:39:46: --> 250-AUTH=LOGIN
Mon 2007-08-27 13:39:46: --> 250-AUTH LOGIN CRAM-MD5
Mon 2007-08-27 13:39:46: --> 250-8BITMIME
Mon 2007-08-27 13:39:46: --> 250 SIZE 0
Mon 2007-08-27 13:39:47: <-- Rset
Mon 2007-08-27 13:39:47: --> 250 RSET? Well, ok.
Mon 2007-08-27 13:39:47: <-- Mail from:<hndse5okfde@cognifast.com>
Mon 2007-08-27 13:39:47: Performing IP lookup (cognifast.com)
Mon 2007-08-27 13:39:47: *  Error: 名称服务器报告域名未知
Mon 2007-08-27 13:39:47: ---- End IP lookup results
Mon 2007-08-27 13:39:47: --> 451 <cognifast.com> is invalid or DNS says does not exist
Mon 2007-08-27 13:39:47: <-- Quit
Mon 2007-08-27 13:39:47: --> 221 See ya in cyberspace
Mon 2007-08-27 13:39:47: SMTP 会话终止（in/out 字节： 71/342）

出现这种错误是正常的，还是哪里设置不对呀

wxhsh

再把反解查询关了吧，不要再问哪里设置了，前两天刚发过图。