Mac Mail/Spectrum/Charter email issues

I've had an ongoing problem with my Charter (Now Spectrum-they are also my internet provider which may be part of the problem) email accounts working with Mac Mail. Used to be issues sending (would be stuck in Outbox) and now I can't set up a new profile properly when I try to fix the problem by reestablishing a connection. I have tried every different combo provided by Spectrum/Charter as well as several others off of forums, including different outgoing/ingoing, using Mobile settings, and doing a test profile on my Mac. I've wasted 1/2 a day on this with Charter/Spectrum and Apple and even drove an hour to get a new cable modem.

This is regardless of which Mac in our household I try to use.

2 out of 3 techs on both the Apple and Spectrum side have told me there are issues between the two servers, and they point the finger at each other. I've been told this has been ongoing for at least 4 weeks, and both sides say they are "working on it", but there is no assurance of resolution. For now, I have to use IOS devices (where things work fine-crazy!) and web-based email to get my Charter accounts working properly.

I'm not sure there are solutions right now, so I'm posting this just so other frustrated users can find this same update and not waste 1/2 a day or more like I have.