The userid and password for a mailbox are set when a mailbox is setup.  As a general rule, the userid is the portion of the email address before the @ sign.  Ex. For mailbox info@yourdomain.com the userid would be info.  The password is whatever was entered when the mailbox was setup.  If you forget your password you will need to reset it in the Mail Control area (see How do I change an emailbox password?).  Passwords are encrypted after being entered and cannot be looked up in the Control Panel.  Mail servers, both incoming and outgoing, are yourdomainhere.com.  Refer to your hosting setup letter if you are unsure what mailservers you should be using.