This still did not work. I already had all those settings selected. I am running classic Outlook (not "new" Outlook) on a PC. This mailbox has very limited contents - I created another mailbox that has all my saved items, and that one does not receive or send. So the one that hangs has only about 100 newer emails, plus my Sent Items folder, which is at 132 MB right now. I empty the Trash folder every few days and there is nothing in the rest of the folders.
The hang on Synchronizing Inbox problem occurs intermittently. I can still receive email as webmail on my Comcast account as well as on my iPhone native email app. Sometimes I can clear it by using CTRL-ALT-DEL and the End Task function, but even that is not working now. Any suggestions welcome. Thank you.