经过2个小时的琢磨，现已成功安装上
按管理员所说的，也一样会出现上面所说的问题，postadmin还是一样访问不了，提示还是和上面的一样

下面我说下我的步骤：
1.先安装AMP环境，AMP环境工作正常，会出现postadmin还是访问不了，提示：The requested URL /postfixadmin was not found on this server.你只需把postfixadmin-2.2.1.1复制到/var/www/html/目录下重命名为：postfixadmin并给755的限,再访问就可以访问了
2.这一种方法，按管理员所以，先不要架AMP环境，在这种情况下，会出现在访问phpmyadmin postfixadmin时提示：The requested URL /postfixadmin was not found on this server.，页面不存在。解决方法是把phpmyadmin postfixadmin目录都复制到/var/www/html/目录下，关把权限修改成755，解决

个人感觉：
1.0.5.1比0.4版，webmail漂亮些，而且访问速度更快，多了一种webmail访问的方式（squirrel）
2.安装起来比0.4版更容易

个人推荐安装方式：
1.熟悉AMP环境的，选择先安装AMP环境，再安装Iredmail,这样可以选择安装高版本的apache php mysql,因为iredmail里面安装的版本相对较底
2.新手，直接安装iredamail，这样虽然amp版本较底，但可以省去很多配制的麻烦

非常感谢，问题已经解决

总结下个人经验：日志文件不要随便改动

其实这个问题,只是下载时源服务器忙或者联接不上,或者你本地的网络不稳定都有可能出现这种问题的,我也遇到过,呆会再试就能下载了

安装的时候提示：
Transaction Check Error:
  file /usr/lib/php/modules/fileinfo.so from install of php-pecl-fileinfo-1.0.4-1.el5.rf.i386 conflicts with file from package php-pecl-Fileinfo-1.0.4-3.el5.centos.i386

这跟硬件是没关系的

[root@www ~]# cat /etc/amavisd.conf

# Add dkim_key here.
dkim_key("moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");

# Note that signing mail for subdomains with a key of a parent
# domain is treated by recipients as a third-party key, which
# may 'hold less merit' in their eyes. If one has a choice,
# it is better to publish a key for each domain (e.g. host1.a.cn)
# if mail is really coming from it. Sharing a pem file
# for multiple domains may be acceptable, so you don't need
# to generate a different key for each subdomain, but you
# do need to publish it in each subdomain. It is probably
# easier to avoid sending addresses like host1.a.cn and
# always use a parent domain (a.cn) in 'From:', thus
# avoiding the issue altogether.
#dkim_key("host1.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
#dkim_key("host3.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");

# Add new dkim_key for other domain.
#dkim_key('Your_New_Domain_Name', 'dkim', 'Your_New_Pem_File');

@dkim_signature_options_bysender_maps = ( {
    # ------------------------------------
    # For domain: moyeamedia.com.
    # ------------------------------------
    # 'd' defaults to a domain of an author/sender address,
    # 's' defaults to whatever selector is offered by a matching key

    'postmaster@moyeamedia.com'    => { d => "moyeamedia.com", a => 'rsa-sha256'                                                                             , ttl =>  7*24*3600 },
    #"spam-reporter@moyeamedia.com"    => { d => "moyeamedia.com", a => 'rsa-sha                                                                             256', ttl =>  7*24*3600 },

    # explicit 'd' forces a third-party signature on foreign (hosted) domains
    "moyeamedia.com"  => { d => "moyeamedia.com", a => 'rsa-sha256', ttl => 10*2                                                                             4*3600 },
    #"host1.moyeamedia.com"  => { d => "host1.moyeamedia.com", a => 'rsa-sha256'                                                                             , ttl => 10*24*3600 },
    #"host2.moyeamedia.com"  => { d => "host2.moyeamedia.com", a => 'rsa-sha256'                                                                             , ttl => 10*24*3600 },
    # ---- End domain: moyeamedia.com ----

    # catchall defaults
    '.' => { a => 'rsa-sha256', c => 'relaxed/simple', ttl => 30*24*3600 },
} );

# Set listen IP/PORT.
$notify_method  = 'smtp:[127.0.0.1]:10025';
$forward_method = 'smtp:[127.0.0.1]:10025';

# Set default action.
$final_virus_destiny      = D_DISCARD;
$final_banned_destiny     = D_PASS;
$final_spam_destiny       = D_PASS;
$final_bad_header_destiny = D_PASS;
# Add dkim_key here.
#dkim_key("moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");

# Note that signing mail for subdomains with a key of a parent
# domain is treated by recipients as a third-party key, which
# may 'hold less merit' in their eyes. If one has a choice,
# it is better to publish a key for each domain (e.g. host1.a.cn)
# if mail is really coming from it. Sharing a pem file
# for multiple domains may be acceptable, so you don't need
# to generate a different key for each subdomain, but you
# do need to publish it in each subdomain. It is probably
# easier to avoid sending addresses like host1.a.cn and
# always use a parent domain (a.cn) in 'From:', thus
# avoiding the issue altogether.
#dkim_key("host1.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
#dkim_key("host3.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");

# Add new dkim_key for other domain.
#dkim_key('Your_New_Domain_Name', 'dkim', 'Your_New_Pem_File');

@dkim_signature_options_bysender_maps = ( {
    # ------------------------------------
    # For domain: moyeamedia.com.
    # ------------------------------------
    # 'd' defaults to a domain of an author/sender address,
    # 's' defaults to whatever selector is offered by a matching key

    'postmaster@moyeamedia.com'    => { d => "moyeamedia.com", a => 'rsa-sha256'                                                                             , ttl =>  7*24*3600 },
    #"spam-reporter@moyeamedia.com"    => { d => "moyeamedia.com", a => 'rsa-sha                                                                             256', ttl =>  7*24*3600 },

    # explicit 'd' forces a third-party signature on foreign (hosted) domains
    "moyeamedia.com"  => { d => "moyeamedia.com", a => 'rsa-sha256', ttl => 10*2                                                                             4*3600 },
    #"host1.moyeamedia.com"  => { d => "host1.moyeamedia.com", a => 'rsa-sha256'                                                                             , ttl => 10*24*3600 },
    #"host2.moyeamedia.com"  => { d => "host2.moyeamedia.com", a => 'rsa-sha256'                                                                             , ttl => 10*24*3600 },
    # ---- End domain: moyeamedia.com ----

    # catchall defaults
    '.' => { a => 'rsa-sha256', c => 'relaxed/simple', ttl => 30*24*3600 },
} );

# Set listen IP/PORT.
$notify_method  = 'smtp:[127.0.0.1]:10025';
$forward_method = 'smtp:[127.0.0.1]:10025';

# Set default action.
$final_virus_destiny      = D_DISCARD;
$final_banned_destiny     = D_PASS;
$final_spam_destiny       = D_PASS;
$final_bad_header_destiny = D_PASS;

@av_scanners = (

    #### http://www.clamav.net/
    ['ClamAV-clamd',
    \&ask_daemon, ["CONTSCAN {}\n", "/tmp/clamd.socket"],
    qr/\bOK$/, qr/\bFOUND$/,
    qr/^.*?: (?!Infected Archive)(.*) FOUND$/ ],
);

@av_scanners_backup = (

    ### http://www.clamav.net/   - backs up clamd or Mail::ClamAV
    ['ClamAV-clamscan', 'clamscan',
    "--stdout --disable-summary -r --tempdir= {}", [0], [1],
    qr/^.*?: (?!Infected Archive)(.*) FOUND$/ ],
);

# SpamAssassin debugging. Default if off(0).
# Note: '$log_level' variable above is required for SA debug.
$sa_debug = 0;

# Modify email subject, add ''.
#   0:  disable
#   1:  enable
$sa_spam_modifies_subj = 1;

# remove existing headers
#$remove_existing_x_scanned_headers= 0;
#$remove_existing_spam_headers = 0;

# Leave empty (undef) to add no header.
# Modify /usr/sbin/amavisd file to add customize header in:
#
#   sub add_forwarding_header_edits_per_recip
#
#$X_HEADER_TAG = 'X-Virus-Scanned';
#$X_HEADER_LINE = "by amavisd at $myhostname";

1;  # insure a defined return

是的，因为以前服务器出现过一次问题，很多服务都运行不了了，IredMail装了好多次才装上去的，装了好几天才成功，可谓痛苦呀，而且这方面的资料又比较少，只能自己不断的重复摸索

[root@www ~]# grep 'dkim_key' /etc/amavisd.conf
# Add dkim_key here.
dkim_key("moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
#dkim_key("host1.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
#dkim_key("host3.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
# Add new dkim_key for other domain.
#dkim_key('Your_New_Domain_Name', 'dkim', 'Your_New_Pem_File');
# Add dkim_key here.
dkim_key("moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
#dkim_key("host1.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
#dkim_key("host3.moyeamedia.com", "dkim", "/var/lib/dkim/moyeamedia.com.pem");
# Add new dkim_key for other domain.
#dkim_key('Your_New_Domain_Name', 'dkim', 'Your_New_Pem_File');

我用的系统是Cent OS 5.3

service amavisd start
Starting Mail Virus Scanner (amavisd): Error in config file "/etc/amavisd.conf": Can't open PEM file /var/lib/dkim/moyeamedia.com.pem: Permission denied at /usr/sbin/amavisd line 536.
                                                           [FAILED]
这个服务对收发邮件是否有影响？

在etc/group文件里可以看到
vmail:x:2000
dovecot:x:97
这些跟postfix相关的组都存在