After purchase a hosting package, hosting company will send you an email of server IP, Cpanel login, FTP password together with webmail login URL. For those who not receive the email please contact hosting provider for help.
Example login URL http://www.cus8.com:2095/
Most of the linux web hosting offer three various interface of webmail for you to choose from; Horde, SquirrelMail, and RoundCube Webmail. Regardless which option you choose, the mail content remains no change.
The comparison Horde, SquirrelMail, and RoundCube:
RoundCube webmail – clean and nice interface
SquirrelMail webmail – most basic interface
Horde webmail – clean interface with calendar management feature