hello,
Any recommendation for webmail script? Right now i am using cpanel and i found the webmail in there are not user friendly, it request user to type username and domain (eg. nick@domain.com) . Is there any script allow the user to type username only instead in full?

Thank you

What's not user friendly about the cpanel webmail?

You might want to try roundcube - www.roundcube.net

Also, squirrelmail is pretty much idiotproof.

Give roundcube a try, it's amazing (requires IMAP in your server)
If you are hosting several domains and want to use the same PHP code for all of them, you'll need to "hack" the login form to pick up the domain's e-mail from the URL. You can have also a combo-box to select the domain.
For a single domain is much simpler.