qmail 不能发邮件问题

@4000000044eaa5243b179a04 delivery 1589: success: 139.175.252.15_accepted_message./Remote_host_said:_250_OK_id=1GFPos-000DlZ-L
s/
@4000000044eaa5243b188c34 status: local 0/10 remote 4/20
@4000000044eaa53e1f7e1c64 delivery 1595: success: 202.43.216.28_accepted_message./Remote_host_said:_250_ok_dirdel/
@4000000044eaa53e1f7fed3c status: local 0/10 remote 3/20
@4000000044eaa53e1f80c02c end msg 1142975
@4000000044eaa57e055adb74 delivery 1597: deferral: Connected_to_61.221.179.247_but_sender_was_rejected./Remote_host_said:_451_

@4000000044eaa57e055b0a54 status: local 0/10 remote 2/20
@4000000044eaa57e05613c44 delivery 1598: deferral: Connected_to_61.221.179.247_but_sender_was_rejected./Remote_host_said:_451_

@4000000044eaa57e05615f6c status: local 0/10 remote 1/20
@4000000044eaa58005374de4 delivery 1596: deferral: Connected_to_61.221.179.247_but_sender_was_rejected./Remote_host_said:_451_

@4000000044eaa58005377cc4 status: local 0/10 remote 0/20
@4000000044eaa5a53494616c new msg 1142792
这是日志记录内容，意思是不能解析dns，他那边可以发邮件给我的，但是我不能发邮件给他，显示的日志是这样的，后来发现他们那边解析不了我们邮件服务器的地址，调试后一切OK了。