一般的邮件列表该如何回复？？

只用过google groups
订阅了传统的邮件列表后，完全不知道该怎么回复...
该邮件列表在有用户发送邮件后，会向订阅了该邮件列表的用户发送一封如下格式的邮件
标题：Users Digest, Vol 30, Issue 1
发件人：[email protected]
收件人：[email protected]
正文
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Today's Topics:

1. AAABBB
2. CCCDDD


----------------------------------------------------------------------

Message: 1
Date: Fri, 5 Apr 2013 12:29:41 +0520
From: Arun G Nair <[email protected]>;
Subject: Re: [gruupname] AAABBB
To: aaaa <[email protected]>;
Cc: [email protected]
Message-ID:
<CA+k2VZ3+Z_qBt0HdVJBRNGE=pretFE7dYCLD1gxKYqA7ZXxWRQ@mail.gmail.com>;
Content-Type: text/plain; charset="iso-8859-1"

邮件内容

--
::: Keep Smiling :::
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End of Users Digest, Vol 30, Issue 1
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这种格式的邮件列表该如何回复？？
因为回复过一次，结果原本应该是
aaaaa
--re: aaaaa
----re: aaaaa
却变成
aaaaa
--re: aaaaa
re:aaaaa
变成另一个主题了...