showe1996, if all you're really after is a mail server and a sinlgle site, have you seen this: http://flurdy.com/docs/postfix/
To answer a questin or two you've raised:
I only can get to a page saying
"welcome, this IP address is shared. Please login to www.mysite.dom to see the website you are looking for."
My questions are:-
1. Is this normal ?
2. Can I get around the problem ?
The page tells you you have ISPConfig set up. It is the index.html splash page for people who have a domain DNS pointing at your IP, but no domain actually set up in there yet. This splash page default changes when the domain is set up, but has no pages of its own yet. So the answer to 1 is "Yes".
2. You change it by designing a new splash page and uploading it. In Apache2 on a Debian type distro, that's /var/www/apache2-default/ - I have yet to work out where to put it for a domain which is configured but no pages yet.