Any email account that you have established in Mail will be automatically be setup on you iPhone when you use iTunes to activate it or the next time you synch it. It would appear that CompuServe allows POP3 access to CompuServe Classic email accounts, but not to CompuServe 2000 accounts. AFAIK, CompuServe 2000 accounts such as misterme@cs.com can be accessed only via the Web or via CompuServe's software.
Compuserv
People using Compuserve 2000 should use smtp.cs.com.
People who use CompuServe Classic, Versions 4.02 or less, use smtp.compuserve.com.
I used smtp.compuserve.com for outgoing mail instead of the default setting for the aol accounts for my wife's compuserve account. She normally uses webmail to access her email.