Oh, I see that you replaced an earlier screenshot. I see better now.

Are these POP or IMAP accounts? Are you accessing your mail through any other app or through webmail?

Let’s try  … 

If you go to webmail for sales@transpo.com, are there messages in the inbox that you do not see in Thunderbird’s inbox for that account?

Then right click on the inbox in Thunderbird, select “Properties”, then “Repair Folder”. Do the missing messages appear?

If not, re-start Thunderbird in troubleshooting mode: Help menu - Troubleshoot Mode … 

Does the problem persist?

If nothing here helps, I will ask others to help.

I just noticed something odd: the inbox highlighted in your last screenshot is not the inbox for sales@transpo.com. It is identified as a local folders inbox, but that would be redundant with your local folders inbox and is not where it should be.

We still have not seen an inbox for an account other than the local folders. Would you please show us what you see after you click on what I called the arrow (>) in any account other than the local folders and then on the inbox?

I am also still curious about an early statement. You said that you can see read messages in a stack and unread messages in a stack and that there is a third stack. Are you doing something to isolate read messages and unread messages? Have you created any message filters?

Do you use anti-virus software?

Was everything working better before the latest update? Did you do anything with this update such as re-creating your accounts or are you seeing only the results of what the update did?

Many questions, I know, and you must be sick of all this. You just want e-mail to work. I wish that I had a magic wand for you.

No problem. Here is how Thunderbird shows today's read mail. There's no remaining unread emails until tomorrow when fresh emails arrive. However, in the meantime, I'd still like to be able to see today's "read" emails, for doing replies etc.

You are still showing us a folder that, as far as I know, should not even exist. So it may not be handling messages properly.

Would you please show us the inbox of an account with a “>” sign? Click on the “>” sign to see the account’s folders. Redact what you don’t want to share.

And answer my other questions?

I guess this conversation is a good example of how difficult Thunderbird can be for an average user. Thunderbird is clearly not for the "average user"! Ideally, we should not be having this conversation because everything would be more or less intuitive. I don't really want to be using so much of your time on my simple problem.

But thanks for your good efforts and trying to explain.

I am happy to spend time.

Thunderbird can be easy to use. There seems to be something very simple that is interfering. I don’t think you are looking at the right folders. Just click on one of those disclosure triangles (>) and then on the folders that appear below the account name (e-mail address). You should be able to see all your read and unread messages. No filters, no searches.

You can learn to do more after that.

A quick filter is set. Click the button with the pin so that the blue mark disappears.

1. The pin only means that filter criteria set in this folder will also be applied to other folders when switching to a different folder, and has no relevance here. 2. I agree with Scooter there is something wrong in your folder view, because "Inbox" should not be appearing by itself. Inbox should be inside an accout name or Local Folders. 3. As mentioned in https://support.mozilla.org/en-US/questions/1502925 does the problem reproduce in Troubleshoot mode? 4. If it does reproduce in Troubleshoot mode, check all your view settings: 4.* DO View > Messages > All from the top menu (File, Edit, View, ...). If you don't see that menu hit the alt key on Windows. 4.* Do View > Threads > All.

These are starting points.

Thanks, Wayne!

1. 1: yeah, I realized that later. :(

OK, I think we're making progress. My email hosting service advised that we needed to install a security package, which they did. That was the problem. Now my mail in Thunderbird is appearing properly. It's not my expertise, so I'm not sure if I could explain it properly. But now my email works OK. I can see both read and unread mail together. I never thought email could be so stressful!

That is why I asked about anti-virus software.

I am glad that Thunderbird is working better for you now.