Well, according to what their own website says, none of those is correct and the incoming mail server name should be imap3.knology.net…

It amazes me how often the support staff at the mail service provider get their own settings wrong and then blame Thunderbird for not being able to connect to the server…

Thanks for the input, while on the phone with the provider we tried 4 different addresses. imap3.knology.net was one of those, also tried it with the two recommended numbers at the end, :143 and :110. Something changed, was there a Thunderbird update? I have four email addresses in my Thunderbird mail program, two With my provider knology and two with gmail. The Gmail are working fine, but the knology do not work.

 Still need help.  Thanks

Can you post a screenshot showing that your incoming mail server settings, including the security settings part, match what the article I linked before says they should be?

I spent another 35 minutes on the phone with my provider, he said the address has been changed although the legacy

has been working. I changed my smtp outgoing to the new 

address and it did not work so I changed back and it does work. Meaning at least the legacy out going address is still a valid address.

In the end the provider was not able to solve my problem. 

His last suggestion was to remove my email from Thunderbird and reinstall it.

Do you think this is a good idea?

If yes, how do I start that?

It has been 11 years since I set this up and I have no recall of how I did that.
                 Thanks for your time.

Thank you! I followed the website you posted (lack of comprehension first time around) and I think the key was restarting the computer. That forced a save and now my email is working. I did get a note to delete some email for lack of memory, which I will need deal with. My access to Usenet stopped a couple years ago.

 Are you up to helping me get my Usenet (newsgroups) working again in Thunderbird?

I find it hard to believe restarting the computer made a difference here. The problem must have been that you simply didn't know for sure what the settings should be and were not configuring Thunderbird properly according to those settings. This is an incredibly common problem and it amazes me how often the blame is put elsewhere…

Anyway, it's not a good idea to reuse a thread to start talking about some other unrelated issue. Better start a new thread with an appropriate subject for the issue you want to discuss there.

The webpage you posted did tell me to restart after I changed the data. Also, the provider did have me try the addresses on their webpage, so I guess we will notknow if that was the key or not. But it is working now! :-) Thanks for the help!