Try rebuilding the folder index with Repair Folder in the folder context menu, Properties.

Thank you, but that actually made it worse, making all of them "Phil Ross" going back more than 5 years. Before, it was just over the last few weeks.

I need to do searches by name sometimes and this makes it impossible, unless I use Outlook or my laptop.

Any other suggestions for getting them back?

Maybe the easiest path is to uninstall & re-install?

Uninstall/reinstall seldom fixes issues in the separate profile folder. But it can't do any harm.

You could try rebuilding the Inbox by following these instructions:

http://kb.mozillazine.org/Compacting_folders#Real_fix

basically, you copy the existing messages to another folder, then close TB and delete the mbox and .msf files for Inbox. When TB restarts, a new Inbox is automatically created and synced with the IMAP folder.

This is definitely a bug with the new Nebula T-bird Version 128, and possibly inter-related to the user's Window version 10 or 11. (See below)

Note about this problem: These problem emails that were being re-named by T-bird/Nebula, were all generated from same source, a Google Workspace email app in my website. Thunderbird changed them all to read the same in both the "From" and "Correspondent" field. This was a problem because I routinely need to refer to them by name, and they're moved to an applicable folder for that reason. No other email was re-named. All email in that folder from the same source was.

Fixing it: When I uninstalled and re-installed the same T-bird version, it didn't fix it the problem. When I uninstalled again, and then re-installed the prior version, 115.13 Supernova, the emails are named correctly. Now it's set to not update.

The strange thing about the original problem is that T-bird is grabbing the source email from the Microsoft Exchange server and changing them. All the above effected T-bird email always displayed correctly in Outlook mail.

May be related to Windows version??? This problem was on my HP AIO desktop running Windows 10. Meanwhile, my HP laptop running Windows 11 also updated T-bird before I could stop it. However, it kept the same emails named correctly, but it added the sender's email in both the "From" and "Correspondents" fields in all emails. Not just the prior miss-named ones. Despite it taking up line space and being redundant, I could have lived with this on the AIO.

When you downgraded from 128 to 115, did you start with a new profile and add the account? If you did, and the names were correct, that is because a new Inbox was created - the same result as the Real fix mentioned above.

In TB 128, the message list display format can be set in Settings/General/Reading & Display.