Instructions for setting up email on the iPhone are located at
http://docs.info.apple.com/article.html?artnum=305882 - the specific information that you will need for Suddenlink is:
a) Account type POP3;
b) Your Suddenlink email address;
c) Incoming mailserver is pop.suddenlink.net
d) Outgoing mailserver is smtp.suddenlink.net
e) No username / password is required for incoming email, but for outgoing email, Suddenlink requires Password Authentication. For these entries, use your email address (NOT your UserID) and your Password.
If you need further assistance with setting up Suddenlink email accounts, please contact Technical Support toll-free at 888-822-5151.