终于成功配置了sendmail为本地用户转发邮件

在ubuntu中安装了sendmail，通过bind在本地管理域student6.org的域名。在给本地用户mailtest发送邮件时，总会收到这样的邮件内容：
From: Mail Delivery Subsystem <MAILER-DAEMON>
To: windy@student6.org
To: postmaster
Subject: Returned mail: see transcript for details
Auto-Submitted: auto-generated (failure)

[-- 附件 #1 --]
[-- 形态:  textplain, 编码: 7bit, 大小: 0.4K --]

The original message was received at Tue, 4 Apr 2006 22:09:59 +0800
from localhost.localdomain [127.0.0.1]

   ----- The following addresses had permanent fatal errors -----
mailtest@student6.org
    (reason: 553 5.3.5 system config error)

   ----- Transcript of session follows -----
553 5.3.5 mail.student6.org. config error: mail loops back to me (MX problem?)
554 5.3.5 Local configuration error
整了好长时间都没有整好，根据上面提示内容“loops back to me”，觉得应该是sendmail没有意识到student6.org是本地的域，开始不相信，因为我已经在/etc/mail/local-host-names中填写了student6.org这一行。后来实在不行，在/etc/mail/sendmail.mc加入一行：
LOCAL_DOMAIN(`student6.org')
来确保这个域被sendmail认为是本地域，终于成功了！SIGN~~~~~~~