We are pleased to provide not just one, but 3 webmail applications! You can use your laptop, or any other computer you have available. Just be mindful that using "public" computers is generally not safe. To access webmail, point your web browser at any of the following URLs:
http://mail.yourdomain.com/
Log in with your email address and password, and click the "webmail" tab. You can try all three webmail clients and use the one you prefer.
You may notice there's an administration tab there as well. To manage email accounts, forwards, and mailing lists for @yourdomain.com, click the administration tab while logged in as postmaster@yourdomain.com. Your postmaster password is the same password as your hosting/FTP password.