Your webmail package is called Horde. To read your email online follow the directions below:
http://webmail.xxxxxxx.xxx
where xxxxxxx.xxx is equal to YOUR domain name.
(ie: http://webmail.abc.com)
Your username and password will be the the ones you specified for your account when your domain was created.
Your Username MUST include the domain name.
(Ex: Username: larry@abc.com)
Then of course your password.