Who is your email provider? You can disable that unread/new icon badge via Preferences. It's a new feature and needs some polishing. With or without the badge, you should still be seeing folder names in bold when they have unread messages in them. If this is not the case, and Thunderbird is NOT fetching new messages from the server, then something is very wrong with your fairly new Thunderbird setup which should be working as it does for millions of other users. I have no idea how you went about migrating to or setting up Thunderbird, so I can only suggest to create a new profile, set up your email account and see how that goes. Thunderbird should be working normally. SeeAutomatic Account Configuration Profile Manager - Create and remove Thunderbird profiles Manual Account Configuration

Right now: 1 Account at GMail; 2 at AT&T; 1 at MXRoute. All IMAP.

TB was installed from the installer downloaded directly from mozilla.org. The individual accounts were set up in TB just following the default add existing mail account process within TB and not changing any of the defaults. The only subsequent change I've made was to change the name of the Junk folder in TB to match the name of the Spam/Junk folder of a couple of the accounts. No other changes. I am using unified folders in TB. On a brand new (completely fresh, completely up-to-date, direct from MS, non-gray market, activated) copy of Windows 10.

After having this problem the first time I installed it after a couple of weeks I [i]completely/i uninstalled TB and reinstalled it and re-added the accounts. Same problems. About a week after that TB auto-updated itself to the version shown in my OP. Same problem.

I can post an example screenshot of what I am seeing but in words (and ignoring the task-bar icon badge): TB will show (or not) a number of messages in the unified Inbox that does not match the sum of messages shown in the individual account inbox sub folders, none of which agree with the number of messages actually shown in the message pane. These numbers will also not in general agree with the totals shown down on the individual accounts - always bold, usually black but sometimes blue - at the bottom of the list. The same applies to the Junk folder.

I have a couple of Macs running Mail.app (I've been suing Mail.app on our Macs for like 12 years now) and a Pixel phone running Aqua Mail (for around 6 years) and I don't, and have never, has any problem with any of those. They are all accessing the same IMAP accounts as TB - in fact they are both accessing a couple of additional accounts that I have not added to TB yet due to wanting to get this problem solved before complicating things more. All those other email clients were also set up just using their default, automated, account setup process - nothing special or custom. So I don't see how the problem is with any of the account providers.

Right now: 1 Account at GMail; 2 at AT&T; 1 at MXRoute. All IMAP.

TB was installed from the installer downloaded directly from mozilla.org. The individual accounts were set up in TB just following the default add existing mail account process within TB and not changing any of the defaults. The only subsequent change I've made was to change the name of the Junk folder in TB to match the name of the Spam/Junk folder of a couple of the accounts. No other changes. I am using unified folders in TB. On a brand new (completely fresh, completely up-to-date, direct from MS, non-gray market, activated) copy of Windows 10.

After having this problem the first time I installed it after a couple of weeks I [i]completely/i uninstalled TB and reinstalled it and re-added the accounts. Same problems. About a week after that TB auto-updated itself to the version shown in my OP. Same problem.

I can post an example screenshot of what I am seeing but in words (and ignoring the task-bar icon badge): TB will show (or not) a number of messages in the unified Inbox that does not match the sum of messages shown in the individual account inbox sub folders, none of which agree with the number of messages actually shown in the message pane. These numbers will also not in general agree with the totals shown down on the individual accounts - always bold, usually black but sometimes blue - at the bottom of the list. The same applies to the Junk folder.

I have a couple of Macs running Mail.app (I've been suing Mail.app on our Macs for like 12 years now) and a Pixel phone running Aqua Mail (for around 6 years) and I don't, and have never, has any problem with any of those. They are all accessing the same IMAP accounts as TB - in fact they are both accessing a couple of additional accounts that I have not added to TB yet due to wanting to get this problem solved before complicating things more. All those other email clients were also set up just using their default, automated, account setup process - nothing special or custom. So I don't see how the problem is with any of the account providers.

Mozilla.org has no download offerings for Thunderbird as far as I can see. Thunderbird's official website is thunderbird.net

Switch from Unified view to All folders view. Are folders with unread messages displayed in bold? Are the unread messages in bold too?

Is Thunderbird downloading new messages at all, for any of your accounts?

Well, according to my web browser it was downloaded from here: https://download-installer.cdn.mozilla.net/pub/thunderbird/releases/91.1.2/win64/en-US/Thunderbird%20Setup%2091.1.2.exe

And that's the location that the green "FREE DOWNLOAD" button at https://www.thunderbird.net/en-US/ links to so... If that's not the correct download location then TB has a much bigger problems than the ones I detailed above. Please let me know if this is the case so I can immediately uninstall TB and scan my computer for other problems.

Yes. TB is downloading messages for all accounts.

That is the correct location, and it's NOT mozilla.org. What is happening to the downloaded messages? Are they automatically marked as read in arrival, so that they never appear in bold as unread? What about the folders they arrive in? Are they not in bold for the unread messages? Are the account names not bold and blue when they get new messages?

That is the correct location, and it's NOT mozilla.org.

Nor is it Thunderbird.net. Seriously, just let it go already. It's not helping.

What is happening to the downloaded messages? Are they automatically marked as read in arrival

No. They are not getting automatically marked as read.

What about the folders they arrive in? Are they not in bold for the unread messages? Are the account names not bold and blue when they get new messages?

Sometimes to both. That's the problem and it is completely inconsistent. See attached example. And this is a mild example.

Switch to the All folders view instead and use it that way for some time to see if the behaviour is the same. Your screenshot shows you're still using the Unified view. If you'd rather not switch, then I have nothing else to suggest. I too use Unified view mostly and the unread count is consistent for all folders and they all show in bold when they have unread messages. I have no idea what else you can do to fix or troubleshoot it.

I didn't just take that screenshot, it's from a couple of days ago so I could show someone else. I'll try turning off unified fodders but I don't think I really want to use it that way - I still have four more accounts to add and having them all separate isn't what I want. Unified folders is basically a requirement. Also, I don't have any problems with any other mail clients so whatever is happening must be TB specific. And it's not like GMail, AT&T and MXRoute are unknown entities.

< rant on> While it is not helping, I would point out that while the Thunderbird project uses many of the facilities of the Mozilla foundation it is not a product of the foundation or the Mozilla corporation that releases Firefox. See https://www.mozilla.org/en-US/firefox/products/ For those of us that have been involved with the project in the years since Mozilla dropped out of Thunderbird development almost a decade ago the public misconceptions about the what and who are grating. I am sorry you perhaps got caught in that frustration, but to be constantly reminded that folks still think of Thunderbird as a Mozilla product is actually somewhat disappointing as only those that have made the leap that it is not a product of Mozilla are financially supporting Thunderbird. Donations to Mozilla do not come to Thunderbird. <end rant>

I have several possibilities in your case, but further diagnostic information would make this guessing game so much easier.

Your unified view search folders are corrupt. But as you have not looked outside that view I and I guess stans can throw it out there as a possibility. Now do you want to go thorough the process of deleting and rebuilding those folders in the off chance they might be borked? Or do you want to try the all folders view and see if it agrees with the unified view before undertaking these additional steps? If the counts agree it is not the individual smart folders that are the problem.

Right click the parent folder (not the sub folders and again in properties look at the folder that are included in the parent counts. Not all folder are displayed. I have 25 folders being searched to populate the list, but only 13 accounts appear in the unified list. In many cases they are sent folders that allow the display of replies in the general mail list in a threaded view.

Or it might be an indexing issue on the base folders. But as you have not tried the all view to see if the counts match up I have no idea. You could repair the base folder just on spec and see if it helps (Right click the folders and select properties and then repair), or you could take the diagnostic steps asked of you and answer with a response that allows the process to move forward.

It may also be that the account message counts are correct and do not include all mail because you do not have all server folders subscribed resulting in apparent discrepancies because you only have partial information to add up from. Have you checked you have everything subscribed (right click the account in all view and select subscribe. Sorry but that is the easiest way. You could wade through the account settings for each account by that is rather slow.

You might also want to right click the spam/junk and trash/deleted folder to ensure they are being checked when the server is polled. They are not normally unless you select the folder, so mail in there will appear in account counts that are not apparent in the folders because those are set by default to not be checked on each get mail cycle but will be included in mail counts provided by the server.

The default badge shows new unseen messages (those that appear with the unseen yellow/gold asterisk in the mail lists). That is not unread message as you appear to be thinking (and certainly posting images showing). I would therefore expect them to be different as they are counting different things. This can be changed in preferences to show a count of unread messages or turned off completely.

Did you already change this preference to show unread mail and have found a discrepancy perhaps? If so you need to make that clear.