I wish I could offer an easy fix, but instead I can say you are not alone. I have seen a few others report the same error, and although there is an old bug that seemed related to Mac OS, the later examples are not just MAC. You could search that exact error text in this forum to find what other people tried, but I have not seen a consistent 'cure'. It is certainly puzzling. So, what is your OS? Were you trying to send/reply or just open the message? Others seeing this error report that the email when opened looks like a message being replied to or forwarded - it opens in write/edit mode. Is that what you see? If you could upload a screenshot that would be useful. Try opening an email a different way - right click and choose open - is the result different? Does it affect all incoming email or only some? Do you have more than one account in Thunderbird, and if so does it affect all accounts or just one? You could edit your SMTP settings, save, close, open, and reset the SMTP settings. Just in case the account identity for sending is not being detected.

I wish I could offer an easy fix, but instead I can say you are not alone. I have seen a few others report the same error, and although there is an old bug that seemed related to Mac OS, the later examples are not just MAC. You could search that exact error text in this forum to find what other people tried, but I have not seen a consistent 'cure'. It is certainly puzzling. So, what is your OS? Were you trying to send/reply or just open the message? Others seeing this error report that the email when opened looks like a message being replied to or forwarded - it opens in write/edit mode. Is that what you see? If you could upload a screenshot that would be useful. Try opening an email a different way - right click and choose open - is the result different? Does it affect all incoming email or only some? Do you have more than one account in Thunderbird, and if so does it affect all accounts or just one? You could edit your SMTP settings, save, close, open, and reset the SMTP settings. Just in case the account identity for sending is not being detected.

REPLY: 1. My OS is Windows 10 2. I can see and open messages in my Inbox but they no longer are configured to "reply" or "forward". 3. When I do click "Ctrl O", emails open as in the past and I can reply or forward as before, but I sure don't want to have to do that for every email going forward just because a Thunderbird update 'left me with a glitch'! 4. When I open messages, they don't open like a message being replied to or forwarded (as stated above, those options aren't available any longer, rather, my email address is showing in the "To" line, not as write/edit mode. 5. It is affecting all emails in my Inbox now!! 6. How do I edit my SMTP settings and what are the chances that will change anything? I'm not very computer literate when it comes to that sort of admin! 7. Under the circumstances, a screenshot wouldn't show anything I haven't outlined, and I'd rather not expose the information in my Inbox in such a public forum (I think I've covered everything above?) I do hope someone might have the answer soon. Thanks for your time!

Hi Thank you for the detailed answers. There are not many people with this issue, which makes it hard to trace a cause. Clearly not a Mac keyboard issue in your case. 6. Edit SMTP - All I want to do is force Thunderbird to refresh those settings without changing anything permanently. It worked for another person recently, but no guarantee it will work for your situation. https://support.mozilla.org/en-US/kb/cannot-send-messages#w_verify-your-smtp-outgoing-email-settings In the Thunderbird menu bar, click the Tools menu and select Account Settings, or click the Application menu button (3 bar), select Options and Account Settings from the sub-menu, and select Outgoing Server (SMTP) from the bottom of the list in the left panel. Click Edit, and change something minor like the description or port number. Save, and close Thunderbird. Open Thunderbird and set that change back to normal. Save, close and open again, then try opening an email. Please report the result. 7. A picture often does help, and I would recommend you obliterate personal details such as account name and any sender/recipient or subject details. If you use Windows - Snipping tool - you can easily outline the part you want to capture, and edit out those details with the pen function before saving the image. However, that's up to you of course. Even if you don't use that information now it's good to know how to!

6. I did this process twice, 2 different ways, no change. I even rebooted my pc.

7. My Inbox looks the same way it always has, the only thing that has changed is the yellow highlighted text box that is still at the bottom of every item I open even after those steps.

When I right-click on an opened email, in an attempt to choose the 'take screenshot' option, there is no place on my Inbox nor in an opened email where that function becomes available to me. I don't know what the 'snipping tool' in Windows is that you're referring to?

I did open several emails using the 'right click' function (instead of double clicking as I normally do) for opening individual emails and that does work, i.e. "reply" and "forward" etc. functions are available again. I'm guessing, unless we think of something else or it just 'magically' fixes itself in a similar way to how the glitch happened in the first place, I'm stuck having to retrain myself to function without the use the quick double click function. I'm totally open to any more ideas or suggestions! Thanks for your time.

Hi Ok, thanks for trying. That's another option checked off! You say you normally double click to open. Does single click do anything useful for you? Snipping tool is a much tidier way to take a screen shot of a selected part of your screen and save it or email it as an image. It is a Windows accessory, also may be named Snip and Sketch. As I mentioned it has a way to crop (define the area) and edit with a pen or eraser built in. You can just type Snip into the Windows search (click Windows icon in bottom toolbar) or in All Programs or Cortana to find it. Google it if you are interested in finding out how it works.

single (left) click does nothing, only single right click + open in new tab I tried the snip and sketch tool, find it very cumbersome as it won't let me move around to create the shape before saving to the clipboard! too time~consuming compared to a screenshot, but thanks for suggesting it!

Regarding snip, OK - if you screen shot then you need a separate tool like Paint to obscure personal information, while in Snip you can do it in one process. But, that doesn't matter, back to the question. Please confirm you have only one account in Thunderbird using the email address you expect to use - check Options - Account Settings and see if you have multiple accounts in that left column with more than one using the same email address. (I'm thinking about no "unique" identity found). I am going to try to get another expert to look into this.

I have just the one Thunderbird email account, thanks so much for your continued support, so appreciated!!!

Hi, I haven't abandoned you. No success getting anyone to look deeper into this. yet. We already eliminated a few avenues, which leaves me reluctantly looking at deleting and reinstalling Thunderbird. For the moment you're able to function by using [right click] open. If using a device with keyboard, you can also use the keyboard shortcut [ctrl]o, or I think, press Enter when the email is highlighted. Not sure whether those would behave properly or show the same issue as you get with double click to open.

Ok, I think we need more information to move on here. The forum reports you using 64bit windows 10 which makes your operating system basically the same as mine and I see no issue. So first a trial but then other things, so I will number them to make reply easier.

1. Select a message in your inbox, right click it and select edit as new. Now it is up to you. Is there a visual difference between what you get with edit as new and a double click? I am thinking double clicking is acting as edit as new. so please look closely. This does not play out well with the error message as a unique identity should exist in that case. But try it anyway because I am really just trying to set some baselines.

2. Hold the shift key and start Thunderbird, or restart Thunderbird from the help menu entry "troubleshoot mode" continue to troubleshoot mode when prompted. Does the odd double click action continue in this mode?

3. Repeat the troubleshoot startup, but reset menu and toolbars and restart. Still seeing the issue?

4. Now it is back to that help menu. This time the more troubleshooting information. Click the copy to clipboard button and paste it into a reply here on the forum. Make it a reply in which you say nothing, just paste in the information and click post reply. If you have something to say (Like reply to 1 and 2 post it after in another reply. (The forum apparently truncates what you post in troubleshooting information, so the less you say in the same post the more we will actually get)

There is more, but lets see what the troubleshooting information reveals before going on.

Thank you Matt for your message and suggestions 4 days ago. I fully intend to try to walk through the steps you've suggested, it's just that it's rather 'daunting', even though I'm very computer savvy, just not with this sort of thing. As soon as I have the 'brain power' to wade through these steps, I'll send you my comments about the results.

Nothing daunting. lots of words and don't do this. But really

Each of those steps will take perhaps a minute or in the case of the first. Significantly less.

The second, other than an additional dialog on the start up will look like a normal Thunderbird start.

The third is the same as the second, but click the option that is presented to reset.

The last is really just a copy and paste from throubleshooting information to a message just as your last reply here was.

1. No difference in this 'mode'; 2 & 3. Completed these, no change;

Name Thunderbird Version 91.5.0 Build ID 20220106182030 Distribution ID Update Folder C:\ProgramData\Mozilla\updates\8216C80C92C4E828 Update History Update Channel release User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 OS Windows_NT 10.0 19043 Application Binary C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe Profile Folder (Local drive) Build Configuration about:buildconfig Memory Use about:memory Performance about:performance Registered Service Workers about:serviceworkers Third-party Modules about:third-party Launcher Process Enabled Multiprocess Windows 0/0 Fission Windows 0/0 Disabled by safe mode Remote Processes 2 Enterprise Policies Inactive Google Location Service Key Missing Google Safebrowsing Key Missing Mozilla Location Service Key Missing Safe Mode true Profiles about:profiles Telemetry Data about:telemetry

Part one of two and 2 of 2 is is for Firefox :)

Name: Firefox Version: 96.0.1

Can we do the Thunderbird one instead please.

Not sure where my response went, here is the Thunderbird info when I did the troubleshoot step again

Name Thunderbird Version 91.5.0 Build ID 20220106182030 Distribution ID Update Folder C:\ProgramData\Mozilla\updates\8216C80C92C4E828 Update History Update Channel release User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 OS Windows_NT 10.0 19043 Application Binary C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe Profile Folder (Local drive) Build Configuration about:buildconfig Memory Use about:memory Performance about:performance Registered Service Workers about:serviceworkers Third-party Modules about:third-party Launcher Process Enabled Multiprocess Windows 0/0 Fission Windows 0/0 Disabled by safe mode Remote Processes 2 Enterprise Policies Inactive Google Location Service Key Missing Google Safebrowsing Key Missing Mozilla Location Service Key Missing Safe Mode true Profiles about:profiles Telemetry Data about:telemetry

For what it is worth, it is only in the Inbox where double~clicking to open an email produces this message: "A unique identity matching the From address was not found. The message will be sent using the current From field and settings from identity ------------" and disables the "reply", "forward" etc tabs. It doesn't occur if I open a sent message, or an item in my "drafts" folder, etc. Very strange indeed....

Check you have this setting : View > Folders > All

In Thunderbird

• Menu app icon > Help > More Trounbleshooting information
• Under 'Application Basics' - 'Profile Folder' - click on 'Open Folder'

A new window opens showing contents of your profile name folder.

• Exit thunderbird now:

Scroll down, locate and delete the following files:

• folderTree.json
• global-messages-db.sqlite
• panacea.dat
• session.json
• virtualFolders.dat

Click on 'Mail' folder

• If you see this folder - please delete it: 'smart mailboxes'

Start Thunderbird

Do the emails still display as if a draft ?

We are currently trying to identify why some people are having this issue, so your help will be appreciated in nailing down what is going on and potential solutions.

Please try info in my previous comment and provide feedback on the results.

If instructions in my previous comment sound too daunting or If you tried it and still have a problem then try the following:

It is possible the 'Inbox' has got a flag set up as if it thinks it's a draft email. Please try the following:

Install this addon called 'FolderFlags'

• https://addons.thunderbird.net/en-us/thunderbird/addon/folderflags/

How to install addon:

• https://support.mozilla.org/en-US/kb/installing-addon-thunderbird

It adds a tab called 'Flags' in the 'Properties' of a folder.

• Right click on 'Inbox' folder and select 'Properties'
• Select the 'Flags' tab
• if a 'Draft' flag has been set - change it to 'Inbox'.
• click on 'OK'

What did you discover? Did the 'Inbox' have a 'Draft' flag ?

Do emails now display properly?

After trying all other recommendations above, the add-on called 'FolderFlags' recommended above worked for me to eliminate the "A unique identity matching the From address was not found. The message will be sent using the current From field and settings from identity ------------" appearing on opened messages.