Single domain

I just started to learn the basics of linux. I choosed EHCP couse its simple administration settings.
My registration company provides me the DNS seetings, so I only have a fix IP for my domain.
I would like to use some subdomain and the roundcube webmail-system on my host, so what do I need to select at the domain creation and what e-mail settings are nedeed.

I tried to install it two different ways, but the e-mails are not delivered at all.

Thx.

either it is a domain, or subdomain
add with: "easy add domain"
then,
just define your email

if email like: you@yourdomain.com
then, you need to add yourdomain.com to ehcp

after that, just redirect your domain from registrar to your server.

Thx, it works well.
I have a second problem now.
I would like to use the roundcube for webmailing not suirrelmail.
I can use webmail.mydomain.com or cpanel.mydomain.com/webmail to reach squirrelmail login page, but I cant webmail2.mydomain.com (it has standard ehcp blank startpage) or webmail2.mydomain.com/webmail2 for the roundcube. It responds only to webmail2.mydomain.com/ehcp/webmail2/.
Ngix server is not started, it said probably not finished.
Where can I find the config files to set it up the roundcube ?
No apache config found on this.

Thx

Yes i would also like to update my ehcp on my production server, but i am not sure how to upgrade to the newer ehcp with roundcube, but the roundcube part of the install is confusing to me, and i dont want to mess around on the production server without making sure their will be any problems.
i have done many fresh install tests with ehcp and it works fine, but i have problems when i do upgrades.

can you tell me a step by step upgrade progress for ehcp and roundcube or can you install this for me so that their is know error?

for upgrade:
http://ehcp.net/?q=node/1047#comment-2098
http://ehcp.net/?q=node/1076#comment-2209

(in upgrade, do not forget to edit apache2.conf manually. old lines needs to be removed)

for squirrelmail->roudncube (for ehcp 0.29.15 and later):
http://ehcp.net/?q=node/1081#comment-2210

(roundcube does not exist prior to ehcp 0.29.15)

Huge thanx