Hi,
in first way, i am sorry for my easier english.

I'm really amateur with linux - debian server installation and configuration, but i need one for my customers, so I:

1. bought VPS with preinstalled Debian
2. install apache, php, mysql and any other required necessary packages.
3. installed ispconfig - dont know what fill to "Full Quality Host Name / Domain Name", so there are few versions
4. uninstall (maybe, sure not completly) ispconfig
5. install ispCP few times - dont know what fill to "Full Quality Host Name / Domain Name", so there are few versions (any other FQDN/HN from ispconfig too)
6. now, there is ispCP, apache runs good, there are few projects
7. I am really freak from mail server configuration - my friends says, when he installed ispCP, mail server, e-mail runs well... but it is not my case..
8. there is crazy ballast, muddle for me in that system - dont know, what service is active, what mail server have i configure (postfix, vmail, courier,..?)
9. what is best way for that? reinstall system? (there is problem with projects and long-time interruption, while i again install all the services - dont know which one - i had a big problem to install it to this "version"), or is it possible (please, is it possible? ) ) to just reinstall ispCP config without data lose (i dont want to copy all the projects, databases etc.) and new install will configurate all the services (mail server) well?
10. where is problem the mail server is not configured well? is it that FQDN/HN.

I am really glad for any answer,
Thank you!