Problems between Thunderbird and Mediacom Connections Refused

You do get an error for mail.mediacombb.net. However, your server settings use imap.mediacombb.net, and smtp.mediacombb.net respectively. So obviously there is a mismatch, which may be part of the problem. I don't know which server name is correct, you'll have to check with MC.

Beyond that, the certificate for imap.mediacombb.net is a mess. It uses outdated TLS versions, and is vulnerable to certain attacks. See https://www.ssllabs.com/ssltest/analyze.html?d=mail.mediacombb.net

Thunderbird does not accept TLS 1.0 or TLS 1.1 by default. Starting with Thunderbird version 78, support for TLS 1.0 and 1.1 was deprecated and disabled for security reasons, making TLS 1.2 the minimum required version.

If I were you I'd find a new email provider who know what they are doing.

MC tech informed me that M$ Outlook is more friendly than TB.

That somehow fits into the picture. As opposed to Outlook, Thunderbird is more strict in enforcing security. Outlook prioritizes convenience over security, so it potentially puts you at risk. And so does MC it seems.

I forgot to mention that the firewall was disabled for a week. Your reply helped a lot. I do understand about switching to a different ISP. The problem is that MC has the highest speeds Up/Dn. I forgot to add this link that they use at Mediacom Server Settings as you will see what I used for months before TB changed. I even attempted to change from mail to smtp just to test with no luck. I understand Thunderbird"s security concerns. However, this decision does affects us users trying to do away from M$ Outlook. If there is a better e-mail client similar to/than TB for Linux, for free, I have not found it, yet. As for the IMAP issues that you mentioned, I will contact MC and see if I can get to the top tier support and share your information. If it does resolve my problem with TB from MC, I will share soon. Thanks for taking your valuable time to answer. Much obliged.

Judo, you could keep Mediacom as your ISP and use a different e-mail service provider.

Well, I contacted Mediacom and informed them about your statements. Supposedly she will inform the team even though they do not support third party. I told them that their decision(s) will affect other customers who use Thunderbird (TB) with Mediacom.

For two days now, I have not had any issues with TB "connection refused" after I changed the settings. What works now is set to: IMAP Mail Server: mail.mediacombb.net 993 SSL/TLS Normal Password and SMTP Server: smtp.mediacombb.net 587 STARTTLS Normal Password

Again, the "test connection to server" in Account > Server Settings > Security Settings, resulted much better on all four e-mail accounts with MC. Thanks for your input Chris1 as well as Rick. Much obliged.

Have a pleasant day.

Message deleted by user.

I found in the last week just before 9:00 PM until after 9:00 AM, the "test connection to server" responded with a "refused connections," as usual. I had not noticed the times until recently after the initial posts. I contacted Mediacom for the 5th time and informed them of the issue. They still blame Thunderbird and deflected the real issue when I informed them about the grade "F" issue with their certificate. Tonight until early morning hours, I will continue to do screenshots. Second, the IMAP to a totally different e-mail account and name still works flawlessly so I know that it is not Thunderbird. He kept saying check on "M$ Outlook." I did not have the opportunity to explain that I exited Windows environment entirely for two months. Lately, CachyOS is my latest distro that is great for my laptop. What I need is to test the IMAP connection via Terminal to see why the connection was/is refused. UFW has been disabled since = no difference. Thanks in advance for helping or taking your valuable time to read my posts.