Unable to add a comcast.net Account to Mail

I gave up on using my old comcast.net email account years go because of infinite spam. I want to add it back to Mail on my M1 Mini and no matter what I do, adding the Account results in "Unable to verify account name or password." I know my Comcast email address and password are correct because I can get access to Comcast mail in Safari. Also, I successfully added it to macOS Mail on my M2 MacBook Air earlier today without issue. So, I am assuming there is some "residue" parameter or configuration file on my M1 Mini (my main computer) screwing things up. Where would I find Internet Account configuration files on my M1 Mini for mail to check on this theory? Cannot add it to iOS Mail either. Nothing makes sense to me at the moment.