It is well past 9 AM ET and nothing has happened. In any case, it would be nice if Cox would inform us about such activities, preferably in advance, and their periodic progress in an easily accessible web page which would save us a lot of headache and wild goose chase. Otherwise whenever I have contacted Cox tech support, their standard reaction has been to suspect my setup, suggesting needless actions and causing frustration.
Following the suggestions made by several members I turned off SSL in Thunderbird for all my accounts and they are all working - for now anyway. Thanks to them all. It also pulled a bunch of messages from the Inbox of Webmail but not Sent messages.
After turning off the SSL, pop.cox.net had begun to work again but became extremely slow. So I just turned SSL on and email receiving has become fast again. Looks like whatever was wrong has corrected itself and without a single setting change on my part. Hope my luck holds.