You can access your email account using webmail from any web enabled computer or device.
Simply go to your domain name followed by :2096, for example;
Then, you will be shown the following screen:
Enter the email address you want to check, and your password. Once logged in, you are taken to your account page.
At the top left of the page you will see the following option;
Simply click the Open button to begin. To speed things up next time you log in, simply tick the box and RoundCube will open automatically next time you log in.