Can't send/receive email
Norton Support investigated this problem by remote sessions on my system. They tried some things and captured some files and said they would get back to me. They did call a few days ago and left a voice message, but the speech was so rapid my old ears could not understand it.
Today I was applying some opsys and driver updates on one of my Win 11 Dell XPS 13 laptops. After doing that I ran LiveUpdate and restarted the system. On a hunch I enabled VPN and started Outlook 365, just to see if anything changed.
This time Outlook Send/Receive worked without error! And it works with or without the Split Tunneling exclusion of Outlook.exe. I was also able to recreate this success on my backup Dell XPS 13 laptop.
Although I haven't heard this officially, my guess is that they created and implemented a fix, which I picked up via LiveUpdate.
Whatever happened, I now consider this problem to be resolved.