Tried one more thing: Running MS Outlook Inbox Repair Tool. It found and fixed about 500 unspecified errors. Outlook runs a bit snappier now. But no change with regard to this problem. Mail goes to my mail server, as always, but the messages never get sent to Outlook anymore.

I can send messages from Outlook, and the copy stays in my Inbox as it normall does. But I don't know if anyone has replied until I open my browser and login to webmail for each individual email account. And I don't know what's happening to messages that go to the email address provided by my ISP. (I'll have to check their webmail as well.)

Unless anyone has a better idea, I'm going to have to delete every Outlook "rule" and start from scratch. And, frankly, I'm inclinded to never use them again. My AV should take care of malware, as it does now. I'd rather have all the spam end up in my Inbox and have to delete it manually than have to hunt for my legit messages in several different places all day. At this point, it's just a question of which is the bigger hassel.