系统退信

xxxr10001

各位大虾，帮忙解决一下系统退信的问题。昨天，公司一员工不能利用outlook2003发mail到ling@YYY.net.cn, wen@YYY.net.cn，于是我就叫她往我的163邮箱发一封试试能不能发出，并将退信的报告转发给我看看。
她尝试了能成功发到我的163邮箱，本人是菜鸟，经验不足，看了退信的报告仍不知从何下手去解决，遂将退信报告贴出如下，请给位给予指导：

主题: Delivery Notification <elaine.ling@YYY.net.cn, carolyn.wen@YYY.net.cn>
This is a delivery status notification, automatically generated by MTA mail.XXX.com on Mon, 19 Jul 2010 11:11:26 +0800 Regarding recipient(s) : ling@YYY.net.cn, wen@YYY.net.cn Delivery status : Failed. Did not receive the expected protocol response. (YYY.net.cn).
We have been attempting delivery for 5 times.
Maximum delivery tries attempted. Please contact your administrator to contact the destination domain or resend your message. Delivery failed.
Message Information:
Sender     : feng@XXX.com
Recipient  : [email=ling@YYY.net.cn,wen@YYY.net.cn]ling@YYY.net.cn,wen@YYY.net.cn[/email]
MTA Response :510
The original message headers are included as attachment.
退信报告中还有一个附件如下：
Reporting-MTA: dns; mail.XXX.com
Final-Recipient: rfc822; ling@YYY.net.cn
Diagnostic-Code: smtp; 510 Did not receive the expected protocol response.
Action: failed
Status: 5.0.0
Final-Recipient: rfc822; wen@YYY.net.cn
Diagnostic-Code: smtp; 510 Did not receive the expected protocol response.
Action: failed
Status: 5.0.0
（为了不必要的纠纷，小弟将公司的域名用XXX，对方公司用YYY代替）
在线等，渴望得到给位的指点，先谢谢了。

xxxr10001

没人可以帮帮小弟嘛