Okay, my turn ... I am having this problem as well -- after changing the settings according to Verizon's e-mail, Mail (on my MacPro) tells me that the incoming mail server is not responding. The outgoing server works fine -- I've sucessfully sent a test e-mails to other address.
We would need to look at the settings page to make sure its setup properly. If you need to access the messages now until its verified, you can revert back to your original settings. Please send me a private message so we can look at your settings page.