Yikes! It looks even worse than I thought. In addition to all of the emails that were inboxes and outboxes, I lost all of my emails stored in folders.

Please help me recover all of my records.

Note: I have Time Machine running on the Mac. I tried recovering the TB app from a few minutes before everything got screwy and I got the same message about Thunderbird is an app I downloaded from the internet. So using Time Machine to recover an older version of the TB app didn't recover any of my data.

My email address book is empty too.

One more update: I tried recreating my main email account for business. I entered the email address and password. TB looked up the server information and created the account, but that didn't bring back all of the emails that had been stored by TB prior to this happening.

I have TB 145.0 on a Mac. When my trash gets pretty full, I empty the trash then restart TB just to have a fresh start.

This is completely unnecessary: when you empty your Trash folder in TB the corresponding "Trash" mbox file in the profile is automatically reset to 0 kB.

Well, I did it just now and when TB restarted I got a warning that said Thunderbird is an app I downloaded from the internet, do I trust it? First time that has happened.d I clicked on the button that said to go ahead and open it.

This is very odd. macOS only ask this question only once: when you start the first time an application which you have downloaded from internet. Did you download another TB version and replace your actual version?

Anyway, what you report makes me think that you have unwillingly created a new Thunderbird profile, even if your description doesn't allow me to explain how you did it. Now start TB, go to Help > Troubleshooting Information > Profile Folder > Show in Finder, then quit TB. In the Finder window you'll see somewhat like it is shown in my picture. Open the folder "Profiles" and make a screen shot of its contents. Then open the "profiles.ini" file in Text-Edit and make a screen shot of its contents.

Thanks for your reply, Mapenzi.

After sleeping poorly last night – worried that I had lost all my email history – I got up this morning, restarted Thunderbird, and it was back to normal. (Yesterday evening I restarted it at least twice.)

It seems to be working properly now. I did make a screenshot of my profiles as you requested, just in case it has a clue about what went wrong, and maybe a clue about how to prevent it from happening in the future.

BTW, the reason I restart TB each time I empty trash: After I give the command to empty trash, all of the emails in the trash folder are still visible. But after I restart TB the trash folder is empty.

Thanks again!

I got up this morning, restarted Thunderbird, and it was back to normal. It seems to be working properly now.

So everything is fine again!

I did make a screenshot of my profiles as you requested, just in case it has a clue about what went wrong, and maybe a clue about how to prevent it from happening in the future.

Your screenshot shows three default-release profiles and a default profile. The latter might be a very old profile, but possibly it is a "stub" profile created at the same time as the first default-release (the one without a number). Without knowing the chronology of your profile creation dates, without knowing how many profiles you use actually and without seeing the contents of the profiles.ini file it is impossible to tell their "story" nor what exactly happened yesterday when you restarted TB after emptying the Trash folder.

After I give the command to empty trash, all of the emails in the trash folder are still visible. But after I restart TB the trash folder is empty.

Most times I empty my trash folders before they "get pretty full" which means for me before they contain thousands or more deleted messages. So when I empty a trash folder containing a hundred or so messages the effect is immediate. I might compare your TB trash folder with my Mac's trash bin: sometimes it contains many thousand files and folders and emptying would take half a minute or more.