help me

photo

我用的是rd9
没有修改任何配置文件启动sendmail（启动正常），然后
telnet localhost 25
结果如下：
[root@localhost mail]# telnet localhost 25
Trying 127.0.0.1...
Connected to linux.com (127.0.0.1).
Escape character is '^]'.
220 localhost.localdomain ESMTP Sendmail 8.12.8/8.12.8; Fri, 28 May 2004 16:41:4
7 +0800
helo aa
250 localhost.localdomain Hello linux.com [127.0.0.1], pleased to meet you
mail from:aa@localhost
530 5.7.0 Authentication required



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求救：530 5.7.0 Authentication required
是什么意思，怎样去掉它！！！！