mail.optonline.net is not responding

On my iphone4 my mail just stopped working midweek last week. I have been to the optimum website double checked that all of my settings are correct. I have even deleted the account and recreated it. It still says that "the mail server mail.optonline.net is not responding". Then is says to check my mail settings. If I go to optimum's website I can access my email that way so the account is active. Does anyone have any suggestions. FYI I have not upgraded my iphone to ios7 and do not plan to. I will be getting a newer version of the iphone in the next few months and i have not heard good things about the iphone4 and the newer operating system.