为何通过外网的QQ、雅虎邮箱无法发送邮件到内网的MD邮件服务器？望高手帮忙解决~

rock715

小弟前段时间刚完成邮件服务器，现在情况如下：
1、内网通过自建的邮箱域名(XXX.net)账号可以互相发送邮件；
2、从自建的域名邮箱发送邮件给QQ和雅虎等邮箱也可以成功；
3、从QQ和雅虎等邮箱发送邮件给自建域名邮箱无法接收。例如通过QQ邮箱发送邮件后显示投递成功，但是内网邮件服务器里没有显示接收到邮件的信息，一段时间以后，QQ邮箱收到一封题目为failure notice的邮件。具体类容如下：
Hi. This is the qmail-send program at m-g3.dns.com.cn.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<rock@huasui.net>:
Unable to switch to /usr/home/h/u/a/domains/huasui.net: access denied. (#4.3.0)
I'm not going to try again; this message has been in the queue too long.

--- Below this line is a copy of the message.

Return-Path: <273425774@qq.com>
Received: (qmail 41083 invoked by uid 89); 20 Aug 2010 08:01:54 -0000
Received: from unknown (HELO mailmx.dns.com.cn) (122.70.138.30)
  by m-g3.dns.com.cn with SMTP; 20 Aug 2010 08:01:54 -0000
Received: from smtpbg64.qq.com (HELO smtpbg64.qq.com) ([119.147.10.223])
by mailmx.dns.com.cn (MOS 3.10.7-GA FastPath queued)
with SMTP id LAV44989;
Fri, 20 Aug 2010 16:01:54 +0800 (CST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qq.com; s=s0907;
t=1282291313; bh=9aoyOhkaWvuBoNMWKDa/ypJs1OR2X2m6vK2GjGPax0I=;
h=X-QQ-ThreadID:X-QQ-SSF:X-Originating-IP:X-QQ-STYLE:X-QQ-mid:From:
To:Subject:Mime-Version:Content-Type:Content-Transfer-Encoding:
Date:X-Priority:Message-ID:X-QQ-MIME:X-Mailer:X-QQ-Mailer;
b=CzE4atmfhAU17zHXgJHkYyzTGOvuQjrSLijXvMASz+XaV2z0o8lpEOHSxLP+xgtDY
fRqJ1i9fQ9IaVciCZ0R5Zq+Eo/8c18iHl0PNcXpQmkZ9vCCfJQ3pT7+jh1GPrSZ
X-QQ-ThreadID: 0psNZjKPZ1,0
X-QQ-SSF: 0000000000000040
X-Originating-IP: 124.225.136.36
X-QQ-STYLE:
X-QQ-mid: webmail83t1282291312t5356303
From: "=?gbk?B?wuUgv8s=?=" <273425774@qq.com>
To: "=?gbk?B?cm9jaw==?=" <rock@huasui.cn>,
        "=?gbk?B?cm9jaw==?=" <rock@huasui.net>,
        "=?gbk?B?cm9jaw==?=" <rock@park.goldenname.com>
Subject: 111111111111111111
Mime-Version: 1.0
Content-Type: multipart/alternative;
boundary="----=_NextPart_4C6E3670_093395C0_413C6BD8"
Content-Transfer-Encoding: 8Bit
Date: Fri, 20 Aug 2010 16:01:52 +0800
X-Priority: 3
Message-ID: <tencent_7738E8E075000525051945C2@qq.com>
X-QQ-MIME: TCMime 1.0 by Tencent
X-Mailer: QQMail 2.x
X-QQ-Mailer: QQMail 2.x
X-Junkmail-Status: score=10/50, host=mailmx.dns.com.cn
X-Junkmail-SD-Raw: score=unknown,
refid=str=0001.0A150204.4C6E3672.00B0,ss=1,fgs=0,
ip=119.147.10.223,
so=2009-07-20 21:54:04,
dmn=5.7.1/2009-08-27,
mode=single engine
X-Junkmail-IWF: false

This is a multi-part message in MIME format.

------=_NextPart_4C6E3670_093395C0_413C6BD8
Content-Type: text/plain;
charset="gbk"
Content-Transfer-Encoding: base64

MTIz

------=_NextPart_4C6E3670_093395C0_413C6BD8
Content-Type: text/html;
charset="gbk"
Content-Transfer-Encoding: base64

PERJVj4xMjM8L0RJVj4=

------=_NextPart_4C6E3670_093395C0_413C6BD8--

rods

队列太长，你的邮件太多了

rock715

是指我发送的邮件多导致的么？如果是这样，以前我只发送一封邮件也一样收不到。而且邮件服务器在搭建不久，也没几封邮件。我是新手，希望大侠能细心说下。不胜感激