Using Apple Mail on my iMac, and the SMTP account is connected to the server but the IMAP account remains offline. Have tried everything I can thing of (restart computer, reenter account name and password, try different account names). Nothing seems to work. I'm also getting frequent messages that "mail.mediacombb.net" isn't a valid server.
Thank you for that information. In this situation, if you are getting errors not being able to remove the incoming mail server from your Apple Mail program I would reach out to Apple themselves to troubleshoot their program. If you have any other questions or concerns please don't hesitate to reach out.
I get this error message all the time with Mac Mail on OS 12.6.1 but have gotten it for years. Mediacom blames Apple and Apple blames Mediacom. Can't they talk to each other rather than expecting us to do something about it? Sometimes I get my messages and sometimes I don't. Definitely a problem without a solution.
Problems solved for now. Two problems - IMAP account was offline and the certificate for "mail.mediacombb.net" wasn't trusted. I deleted my account and brought then recreated it. In that process the IMAP account came online and a new certificate was generated by Apple Mail that I could manipulate by changing to "always trust." Keychain now shows three separate certificates for the server and I've trusted each one. This seems to have solved the certificate problem I've had since last summer. (Before this I could not manipulate the certificate that was generated.)