This looks like the bug that's been reported mostly by OS X users:

https://bugzilla.mozilla.org/show_bug.cgi?id=1508153

Does it happen if you right-click a message and Open in Tab or Window? Does it happen in safe mode (hold Shift when you launch TB)? A different mouse?

No.It happens only with messages in the Inbox.I can open those messages in other files or using "open in new tab" and all works well. I dont know if it's a corrupt file or something of that sort. It also happens if I open TB in the safe mode.

I have the same issue. It seems to have started when I went to google gmail and configured something. Since then my inbox emails in TB open with the same error message "a unique identity matching the from address was not found..." I did right click on them and opened in a new window and that helped but they still won't work like they used to, I have another laptop and TB works just fine on it. HELP!!

I also have the same problem and it started a few days ago after I had to reinstall TB, although I haven't changed any of my settings.

For anyone seeing this issue, please answer the questions in my first reply, i.e. safe mode, mouse, right-click. Add your vote or comments to the Bugzilla report, and state your OS and TB versions, keyboard type etc.

Replying to sfhowes...I use windows 10. I have the same laptop...nothing has changed. This just simply started happening. TB simply takes my emails from inbox and formats them for a reply with error message at bottom. Is there something I need to reconfigure? Is it a virus?

So...sfhowes any thoughts on helping us get our TB back to normal? I still have this error 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 XXX@XXX.com" and my emails are annoying to read.

Please note that I only have this problem on one computer. My other two are normal

Reply to sfhowes: my OS is Windows 10 Home version 1809, 64-bits OS TB version: 68.2.2. (32-bit) the problem also happens in safe mode there is no problem when I right-click a message and open it in a new tab or window The problem started at the beginning of this month when I had to reinstall TB from www.thunderbird.net/en-US. Before the reinstall there was no problem at all and I haven't changed any of the settings and all the rest (mouse, keyboard,...) stayed the same.

If you read the bug report, it mentions that the errant window appears when the Enter key on the numeric keyboard is pressed to open a message, but not with the Enter key on the regular keyboard. Some users see the problem when they double-click a message, but not if they use the right-click menu. Your version of windows, 1809, is a year old (current is 1909), yet there are monthly updates that could affect keyboard and mouse performance, which could be a bigger factor than the TB reinstall.

If the problem occurs on just one of your 3 computers, what is different between the three that could explain it?

I never use the enter key to open a message, I always double-click. I only have one computer, it's revlav1 who has 3 computers, I am not that rich.

I have the latest version of windows 10 and the latest updates. I always use the regular keyboard Enter key. You said "Your version of windows, 1809, is a year old (current is 1909)". How do you know that? The problem is only with this computer. I have a desktop and another laptop and TB works fine on them. I also have a gmail account and I'm wondering if there is some setting there. I have tried everything.

revlav1 said

I have the latest version of windows 10 and the latest updates. I always use the regular keyboard Enter key. You said "Your version of windows, 1809, is a year old (current is 1909)". How do you know that?

I was replying to Arend's post where 1809 is stated.

And to let Arend know...I'm not rich...I just have 3 old computers (one isn't mine, it's my work computer) :)