Using classic Outlook for Windows in business environments
For me this problem with the new Microsoft Outlook began on Feb 5, 2025. And at that time, I reached a live body at Microsoft Support who used remote access to my computer to diagnose the problem. After seeing what was happening on my computer, he then put me on hold to talk to his supervisor and came back a few minutes later and said a new Outlook update had broken the interface with Spectrum email and its subsidiary email addresses like my @charter.net address and to wait for a Microsoft update to fix the problem. He said this was a known issue on the Microsoft side.
I have since moved to another desktop email client that works perfectly with my @charter.net email addresses. But seeing that this problem still exists over a month later, I'm guessing there is now finger pointing going on between Microsoft and Spectrum --> "No, you fix it. No, you fix it." And Microsoft being bigger than Spectrum, I'm guessing Spectrum will eventually have to be the one to fix the problem on their end. Or, knowing this is a unique problem with the new Outlook, Spectrum may never make a change to accommodate the new Outlook.