Thunderbird Issues with deleting messages

I am having issues with Thunderbird deleting messages and compacting folders. I’m hoping the readers of this forum can provide some advice. I’m working on a Windows 10 system with the latest Thunderbird. 115.9.0.

Here’s some background: I had a bunch of old Thunderbird email files from the late 1990s/early 2000s that I had saved to a removable drive; and I wanted to see what was in them. So I copied the files (N.B. without their accompanying MSF files) to my Thunderbird profile “Mai\Local Folders”. When I brought up Thunderbird after doing that, Thunderbird created new MSF files and I was able to read the old emails.

So far, so good: But then I decided to delete some of the old emails. Clicking the “delete” button or pressing the DEL key won’t work – that is, nothing happens. Using shift-DEL does work, oddly enough.

I read that a corrupt Trash folder could cause this behavior, so I deleted my Trash folder and MSF and allowed Thunderbird to recreate it. I still could not delete messages normally. I also observed that if I deleted an entire folder, I could not empty the Trash – the “empty trash” function did nothing.

Any of my “normal” Thunderbird folders (i.e., not the ones I created by copying old mail filed) still work normally and I can delete messages; it’s only the ones I just created that display this behavior.

I discovered a workaround: If I create a new folder in Thunderbird, and copy the emails from an old (i.e., 1990s-ish) folder to the new one, I can delete emails from the new folder.

There is also one more interesting quirk: Every single time I bring up Thunderbird, it prompts me to compress files in order to save 261 MB. Evidently the compression isn’t happening.

All of this would seem to point to an issue where Thunderbird thinks it can’t write those old mail folders. I’ve checked the file permissions; I’m the owner and I have full control; I’ve also verified that the same behavior occurs if I deliberately run Thunderbird as an admin (even though my normal user ID is an admin as well).

So the files are definitely writable; but it seems that for whatever reason Thunderbird doesn’t think it can write to them.

Can anyone here shed some light on this odd behavior, and perhaps suggest a better fix/workaround than the one I mentioned?

Thanks for any help you can provide.

– Chris

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