I suggest you use the account settings shown here in Thunderbird. https://www.timewarnercable.com/en/support/faqs/faqs-internet/e-mailacco/incoming-outgoing-server-addresses.html

The server pop-server.ca.rr.com indicates you have not updated your setting to reflect changes made by road runner / Time warner cable

" The RETR command did not succeed. Error retrieving a message. Mail server mail.twc.com responded: no such message. "

Same message. Can send, but not retrieve e-mails. Thunderbird bottom line shows that 137 messages are available. Thunderbird 52.2.1 and Windows 10. HAVE changed server settings to mail.twc.com with proper ports for POP and SMTP. Messages are on the TWC mail server, when I go to it. No virus blockers. Password is correct. Love having folders on my PC- don't want to have to use e-mail server to retrieve mail. Thanks.