I don't think the ISP can help you since they provide support only for your Internet connection which means there is a problem with your connection to the server (in most of the cases, the settings are wrong). Most of the email services that can be used on PC have a web interface as well. Connect to your email using the browser and then check your settings (password, IMAP/POP3 settings, firewall, etc).
Additionally, you can re-configure the account using the built-in wizard.