bold is new unseen mail, read or not is irrelevant. So if you read all mail from bill on your phone and use a filter in Thunderbird to file it in the bill folder the folder will bold with the new mail, even though it has been read.

I understand what you're saying, Matt, but my problem is completely different than what you said above. Okay, here is another explanation. With NO emails coming in, the Local Folders folder Canard will suddenly light up with BOLD font as if there's something "new" in there. Remember that there are no emails coming in and all emails in this and other folders have been read. If I move my cursor over the Canard folder name, after two seconds, it will UNBOLD. Then I will move my cursor away from the name, and about 10 seconds later, it will BOLD again. Now my Local Folders folder Inbox is starting to do the same thing. I think I may have to uninstall and reinstall Thunderbird. What do you think? Or maybe it's an Add-on causing the problem. I'm going to disable all Add-ons and test drive it. Stay tuned.

Okay, I disabled plug-ins and Restarted. "Problem solved." Now I have to figure out which plug-in is causing this problem. Thank you Matt. I think I can handle it from here.

Please post a report of what add-on was the cause of your issue. It helps the next person.

After disabling all plug-ins and powered off, I restarted my computer and Thunderbird in safemode. The problem went away, but after an hour, it came back. This is with all plug-ins disabled!

Then I went to my Inbox and noticed that only emails up to 6/23 were there. Somehow I had lost incoming emails, and possibly others, for 4 days. I decided to do some playing but quickly recovered all those emails by clicking on Get Mail. The previously read lost emails came back Unread, and the Canard folder, which was already bold, got a number in parentheses after it, indicating unread emails. I went through 129 bolded (supposedly unread) emails, verifying I had already read many of them. I finally got to some that had recently been sent and were unread by me. As soon as I read them, the Canard folder name unbolded and I haven't had a problem since then.

I haven't added in the rest of the plug ins yet because I'm still testing this phenomenon for reliability. The problem has gone away, but I'm still testing it, especially with Lightning back. I'll get back as soon as I either detect the problem or it's solved.

Thanks for your help, Matt!

I have encountered the issue if anti virus grabs a mail in transit, but only when I have Tools menu > options > Security > anti virus turned on. It does allow the Av to grab a single mail instead of making a mess of your inbox by grabbing the whole thing.

I went to this security option and noticed that the box was checked for "Allow anti-virus to quarantine individual incoming messages." I'm not so sure I want to uncheck this box, as it says that Thunderbird will check incoming messages for viruses before they are stored locally. I want that feature; otherwise, my AV isn't doing its job.

On the good side, Thunderbird is still working good now that the phenomenon or anomaly mentioned above happened. I still haven't turned on any additional plug-ins in order to fully test this problem. I will probably do so in the next couple of days.