Dear iRedMail Community,
I've found four challenges regarding installation. Thanks for your kind help!

This is the output I get regarding hostnames.
[root@vps ~]# hostname -f
localhost.localdomain
[root@vps ~]# hostname
vps.server.com
I own three email domains. Would the hostname remain server or would I choose one of my existing domains?

[root@vps /]# /etc/selinux/config
-bash: /etc/selinux/config: No such file or directory
[root@vps /]#

how do I disable third-party yum repositories?
how do I enable CentOs official yum repositories?

[root@vps ~]# tar 094 iRedMail-0.9.4.tar.bz2
tar: Options `-[0-7][lmh]' not supported by *this* tar

Dear ZhangHuangbin,

Thanks very much for replying. Wll leave localhost as it is. Succesfully disabled SELinux through the permissive option.

[root@vps selinux]# vi .config.swp
[root@vps selinux]# setenforce 0
setenforce: SELinux is disabled
[root@vps selinux]#

Checked CentOS-Base.repo and everything comes from Centos so I left it intact.

Corrected my previous typo and tar command was succesful. I am now on the blue screen.
This is the first time in my life I install new software on Linux and am very grateful to you for having provided me this opportunity.

Best regards.

Progress a while later: Installation was almost succesful except for the fact that there was a mismatch with the old mySQL password stored at zpanel, which led to errors that I hope have become fixed now that I just restored on my VPS the password originally assigned by zpanel. VPS was rebooted and I read & saved file /root/iRedMail-x.y.z/iRedMail.tips for future reference. Tomorrow I'll continue with section Setup DNS records for your mail server. Congratulations again on this software that really seems the best I've ever seen regarding email.

After iRedMail installation my websites and zpanel went down. I was able to get then back up by accessing mysql through the old password generated by zpanel. I am trying to resume proper installation of iRedMail and at /etc/sysconfig/network inserted HOSTNAME="mlp.riverocooper.com"

Then at /etc/hosts inserted 127.0.0.1 mlp.riverocooper.com mlp mlplocal mlplocal.riverocooper

Then reloaded and hostname continues to be vps.server.com --- and /etc/hosts again reverts to
127.0.0.1 localhost.localdomain localhost mlp.riverocooper.com mlp mlplocal.riverocooper mlplocal
# Auto-generated hostname. Please do not remove this comment.
5.226.169.119 vps.server.com  vps mlp.riverocooper.com mlp
::1         mlplocal mlplocal.riverocooper mlplocal

server.com is not a domain of mine and am unable to remove it.

I would definitely like to have a fresh server so that I can install iRedMail from scratch. My websites are in a secure backup and it would be no problem for me to upload them again if necessary. Please let me know how can I make my server fresh. Thanks very much for your time and precise instructions.

Edited: some DNS conflict caused zpanel to be unaccessible as well as all my sites. I look forward to reinstalling my VPS, perhaps it would be a good idea to take the opportunity to upgrade to Centos 7 and support Nginx rather than Apache in preparation to release of iRedMail 1. I do log in normally to root via putty and my ip address. Also got this while trying to connect to mysql:
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

My VPS provider just performed the necessary changes on localhost and hostname (some restriction prevented me to do them myself). Now I proceed to reinstall iRedMail but probably previous failed installation won't let me. Should I uninstall it first?

[root@mlp /]# tar xjf iRedMail-0.9.4.tar.bz2
tar (child): iRedMail-0.9.4.tar.bz2: Cannot read: Is a directory
tar (child): At beginning of tape, quitting now
tar (child): Error is not recoverable: exiting now

bzip2: Compressed file ends unexpectedly;
        perhaps it is corrupted?  *Possible* reason follows.
bzip2: Invalid argument
        Input file = (stdin), output file = (stdout)

It is possible that the compressed file(s) have become corrupted.
You can use the -tvv option to test integrity of such files.

You can use the `bzip2recover' program to attempt to recover
data from undamaged sections of corrupted files.

tar: Child returned status 2
tar: Error is not recoverable: exiting now

(1) Redownloaded iRedMail-0.9.4 (no 0.9.5 with that name) and installed is as follows:
[root@mlp /]# cd /root/iRedMail-0.9.4/
[root@mlp iRedMail-0.9.4]# bash iRedMail.sh
[ INFO ] Checking configuration file: /root/iRedMail-0.9.4/config ... [FOUND]
< Question > Use it for mail server setting? [y|N]y
[ INFO ] Use config file: /root/iRedMail-0.9.4/config for mail server setting.
[ INFO ] Import installation process status from file: /root/iRedMail-0.9.4/runtime/install.status.
< SKIP > Function: install_all.

********************************************************************
* Start iRedMail Configurations
********************************************************************
< SKIP > Function: generate_ssl_keys.
< SKIP > Function: add_required_users.
< SKIP > Function: web_server_config.
[ INFO ] Configure MySQL database server.
< SKIP > Function: mysql_initialize.
< SKIP > Function: mysql_import_vmail_users.
< SKIP > Function: mysql_cron_backup.
< SKIP > Function: postfix_config.
< SKIP > Function: enable_dovecot.
< SKIP > Function: clamav_config.
< SKIP > Function: amavisd_config_rhel.
< SKIP > Function: amavisd_config_general.
< SKIP > Function: amavisd_import_sql.
Can't open /etc/amavisd/amavisd.conf: No such file or directory.
< SKIP > Function: sa_config.
< SKIP > Function: iredapd_setup.
< SKIP > Function: iredadmin_config.
< SKIP > Function: fail2ban_config.
< SKIP > Function: rcm_install.
< SKIP > Function: rcm_import_sql.
< SKIP > Function: rcm_config.
< SKIP > Function: rcm_plugin_managesieve.
< SKIP > Function: rcm_plugin_password.
< SKIP > Function: sogo_config.
< SKIP > Function: cleanup.
[root@mlp iRedMail-0.9.4]# cd ..

(2)
updated release
[root@mlp /]# cat /etc/iredmail-release
0.9.5

(3) some commands are not found
[root@mlp ~]# tar xjf iRedAPD-1.9.0.tar.bz2
[root@mlp ~]# cd iRedAPD-1.9.0/tools/
[root@mlp tools]# bash upgrade_iredapd.sh
* Detected Linux/BSD distribution: RHEL
* Found iRedAPD directory: /opt/iredapd, symbol link of /opt/iRedAPD-1.8.0
* Found iRedAPD config file: /opt/iredapd/settings.py
upgrade_iredapd.sh: line 322: mysql: command not found
upgrade_iredapd.sh: line 335: mysql: command not found
upgrade_iredapd.sh: line 354: mysql: command not found
* Checking dependent Python modules:
  + [required] python-sqlalchemy
  + [required] dnspython
* Create directory /opt/iRedAPD-1.9.0.
* Copying new version to /opt/iRedAPD-1.9.0
* Copy old config file: settings.py: /opt/iredapd/settings.py -> /opt/iRedAPD-1.9.0/settings.py
* Set correct owner and permission for /opt/iRedAPD-1.9.0: root:root, 0500.
* Set permission for iRedAPD config file: /opt/iRedAPD-1.9.0/settings.py -> 0400.
* Re-create symbol link: /opt/iredapd -> /opt/iRedAPD-1.9.0
* Copy new SysV init script.
* Remove deprecated plugins.
chown: invalid user: `iredapd:iredapd'
* Remove all *.pyc files.
* Restarting iRedAPD service.
iredapd is already stopped.
Starting iredapd ...
* Upgrade completed.
Traceback (most recent call last):
  File "/opt/iredapd/iredapd.py", line 277, in <module>
    main()
  File "/opt/iredapd/iredapd.py", line 248, in main
    p = pwd.getpwnam(settings.run_as_user)

< NOTE > If iRedAPD doesn't work as expected, please post your issue in our
< NOTE > online support forum: http://www.iredmail.org/forum/
< NOTE >
< NOTE > * Turn on debug mode: http://www.iredmail.org/docs/debug.iredapd.html
< NOTE > * iRedAPD log file is /var/log/iredapd/iredapd.log.

KeyError: 'getpwnam(): name not found: iredapd'
[root@mlp tools]#

(4) iRedAdmin upgrade
[root@mlp ~]# tar xjf iRedAdmin-0.6.tar.bz2
[root@mlp ~]# cd iRedAdmin-0.6/tools/
[root@mlp tools]# bash upgrade_iredadmin.sh
* Detected Linux/BSD distribution: RHEL
* HTTP server root: /var/www
* Found iRedAdmin directory: /var/www/iredadmin, symbol link of /var/www/iRedAdmin-0.5
* Found iRedAdmin config file: /var/www/iredadmin/settings.py
* Copying new version to /var/www/iRedAdmin-0.6
chown: invalid user: `iredadmin:iredadmin'
* Removing old symbol link /var/www/iredadmin
* Creating symbol link /var/www/iredadmin to /var/www/iRedAdmin-0.6
Traceback (most recent call last):
  File "delete_sessions.py", line 19, in <module>
    conn = ira_tool_lib.get_db_conn('iredadmin')
  File "/var/www/iRedAdmin-0.6/tools/../tools/ira_tool_lib.py", line 66, in get_db_conn
    print_error(e)
  File "/var/www/iRedAdmin-0.6/tools/../tools/ira_tool_lib.py", line 41, in print_error
    print '< ERROR > ' + msg
TypeError: cannot concatenate 'str' and 'exceptions.ImportError' objects
* Check and install dependent Python modules:
  + [required] json or simplejson
  + [optional] BeautifulSoup
  + [optional] lxml
* iRedAdmin was successfully upgraded, restarting web service is required.
* Restart service (uwsgi) to use new iRedAdmin release now? [Y|n]

(5) LDAP
cd /etc/postfix/ldap/
-bash: cd: /etc/postfix/ldap/: No such file or directory

Will continue going through the rest of the update, however I'm writing to you as I see errors here and there

How can I try restoring my VPS to a fresh OS by myself? Maybe I could give it another try.

Well, I told them that I need to configure iRedMail first and only then I will configure my LAMP server. They agree that it is my VPS and that I have the right to configure any way I want it. For the time being I removed three tars (iRedMail, iRedADP and iRedADmin) and also removed all their uncompressed files and folders. So my root is clean again and will try to reinstall.

My VPS provider are not very knowledgeable on linux, most of their customers use control panel, but they encourage me to learn as much as I can so that I can enjoy my service. Perhaps we'll teach them one thing or two. Thanks Zhang for your continued assistance.

[root@mlp ~]# cd /root/
[root@mlp ~]# tar xjf iRedMail-0.9.4.tar.bz2
[root@mlp ~]# cd /root/iRedMail-0.9.4/
[root@mlp iRedMail-0.9.4]# bash iRedMail.sh
[ INFO ] Checking new version of iRedMail ...
<< ERROR >> Your iRedMail version (0.9.4) is out of date, please
<< ERROR >> download the latest version and try again:
<< ERROR >> http://www.iredmail.org/download.html
I do not find any fresh iRedMail-0.9.5 version to download.

[root@mlp ~]# ls -l
-rwxrwxrwx  1 root root   30168 Jul 29  2013 installer-10-1-0-centos-64.sh.x
-rw-r--r--  1 root root   23374 May  4  2014 installer-10-1-0-centos-64.sh.x.tar.gz

is the installer above appropriate for OS ?

In the mean time I contacted my VPS provider about the possibility of reinstalling fresh OS.

Update at 2:25 pm Eastern Time: Dear Zhang, my VPS provider confirmed they will be happy to reinstall OS for me.

Download the latest version (0.9.5) here:
http://www.iredmail.org/download.html

Good luck and enjoy.

Did you buy your domain names from a domain registration vendor? Does your domain registration vendor host your domain names? Or you have to host DNS service yourself?

BIND was succesfully configured. Changed from NGINX to APACHE because it is easier to find support. All my websites are up. SPF, DKIM and google site verification TXT records were easily added to BIND DNS configuration. Will finally be able to configure and use iRedMail in the next few days. Also upgraded to 0.9.5-1
Do I need to perform any additional step? My saved iRedMail installation still supports nginx, but during the last few days I migrated from nginx to Apache. What should I do to disable nginx for iRedMail and enable apache for iRedMail?