Unable to Configure Email on any Device using any email client

I am unable to configure Outlook for POP or IMAP on Outlook 2010/Windows 7 and Outlook 2013/Windows8...actually I cannot configure it on any device, including my phone or email client. I have four accounts setup with two domains. I have explicitly followed the instructions for setting up both POP and IMAP on numerous clients, numerous devices and my login information is being rejected. I am able to login via webmail so I know my accounts and passwords are correct. I've tried disabling anti-virus but no luck. Any ideas would be greatly appreciated.