You can find the webmail interface for yourdomain.com on

http://webmail.yourdomain.com

and use the account name and password you use to pick up your mail to read it directly from the server

Go to Options on the right-hand panel, then go to Personal Information

The Important line is e-mail address as this is sometimes different from the account name you used to connect to your mailbox, and the account-name is not always a valid email address. The other items are entirely discretionary.