OK, I did what you told me, and even renamed server from moodle.ftniim.org to piks.ftniim.org (I renamed it everywhere) because I have moodle installation under ftniim.org/moodle - just to avoid any confusion between servername and directory name (which will later become subdomain).
Also, I did what is writen at teh end of manual
Rebooted server, deleted and created new mailbox at ftniim.org domain, but I still can't login to http://webmail.ftniim.org/src/login.php
nor I can send mail as root using command mail?
I am confused, what I am doing wrong?
P.S. When I reload apache it says:
piks:~# /etc/init.d/apache2 reload
Reloading web server config: apache2[Mon Oct 15 15:30:22 2012] [warn] NameVirtualHost 18.104.22.168:443 has no VirtualHosts