Webmail is an interface to your commercial email account via the web. It has all the functionality you would expect from a modern email client, including MIME support, address book, folder manipulation, message searching and spell checking. Unlike other webmail clients, its user interface is very much native application-like. This means that it has features like drag-and-drop which you are probably used by applications on your desktop.
Got to http://webmail.(enter your domain here). For example, if your domain is mycompany.com then go to http://webmail.mycompany.com. The site will display the Login Screen for your domain. Simply type in your email address and password.
The screenshot above shows the Login Screen