Internet E-Mail "Enter your user name and password for the following server

For a few months now I get an intermittent pop-up window when trying to receive/send email in outlook 2010. The heading of the pop-up windows says: "Internet E-Mail "Enter your user name and password for the following server," and then there are pre-filled fields for Server pop.cox.net, User Name xxxx Password xxx. When trying to re-enter the data or pressing "OK" or canceling, I get an error and not getting/sending emails. A week ago I changed my password and now I also get errors when trying to access or send the same email via iOS on my wife's iPhone. My settings are correct and my webmail works fine. Both the pop-up window in Outlook and errors in iPhone appear a few times and then all is working fine, until the next time - a few minutes later. I talked with Cox tech support numerous times without a hope for a resolution in sight. The last I heard is that I am still on the "legacy" system and they need to move me w/o knowing when.