There are multiple panes in Thunderbird. Please identify which pane you are referring to. Descripiton at https://support.mozilla.org/en-US/kb/getting-started-thunderbird-main-window-supernova

It's the message list pane, emails don't display subject or from when they appear in the inbox, just the date/time.

In the message pane it looks like the parsing of the headers has broken so you end up with the unparsed/rendered raw HTML as the message view. The first part of the header that is visible in all the ones that don't display correctly for me is something like this:

X-VadeSecure-score: verdict=clean score=0/300, class=clea . X-RazorGate-Vade:

FWIW, it seems to only affect accounts setup as POP3 and not IMAP, and only on Windows and on 140.1.1esr (64-bit). I use one install of TB for multiple accounts a mix of POP3 and IMAP, if I send an email from any one to mixture of the two types, the IMAP ones turn up fine and are readable, and the POP3 ones are gibberish. I downloaded the latest Windows beta and installed it and they look fine in that, and I tried v1.28 on Mint and they look fine in that as well.

I've tried various things such as turning off spam filters, trying a repair on the inbox, deleting the inbox files and letting TB recreate them, nothing has fixed it so far.

Update: Sorry, POP3 emails are NOT fine in the latest TB beta on Windows.

• Start Windows in safe mode with networking enabled - https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode
• Still In Windows safe mode, start Thunderbird in Troubleshoot Mode - https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

Does problem change?

Also..

Only a pop account is affected? Starting immediately upon updating to version 141 or 140.1.1esr (and not before)? What AV software and extensions are used?

Restarted machine in safe mode, TB in troubleshoot mode, tested and emails come through fine, no garbling.

I use BitDefender for AV, but thought I'd ruled out it being that causing the issue by disabling all it's anti-spam or mail scanning features, I could even see the BD headers disappear from emails after I disabled the features.

Do you have quarantine enabled in Thunderbird Settings?

It was yes, turned it off, restarted TB, no change.

I uninstalled BitDefender, and the problem went away, installed a fresh version of BD, and the problem is back, so it looks like it's BD in some way.

It is Bitdefender!! I have had exactly the same problem from 11th August - just with two BT POP accounts - Gmail IMAP is fine. Sending from POP to IMAP is fine - IMAP to POP corrupted. Windows 11 +Bitdefender Internet Security +Thunderbird 128.13.0esr (have not updated for a while!!).

Removed Bitdefender completely (incl. Registry entry) and activated Windows Security - all OK (sigh of relief!!). Re- installed Bitdefender and problem back again. Progressively disabled Bitdefender email protection, antispam, vulnerability, advanced threat - all no change. Disabled all on-line threat and OK. Re-enabled email (incoming) antispam, vulnerability, advanced threat - still OK. Re-enabled all on-line threat - problem back again. Progressively disabled Online threat option - with Encrypted web scan off - OK. All Online threat options on except encrypted - still OK. Encrypted back on - problem back again - Encrypted off - OK!!

Thanks for that I disabled encrypted web scan in my Bitdefender and it's back to normal. Cheers.

Grateful for that - I disabled encrypted web scan in my Bitdefender and it's back to normal. Cheers.

Solution update posted at 8:48 Eastern time (12:48 UTC) Thursday by Alexlandru_BD, an admin at bitdefender, "The developers reverted the changes made in the last signature update and this should do the trick until a permanent fix is deployed. Just click on update in systray and reboot once completed. But keep in mind this change is being rolled out gradually, so it may not reach everyone at the same time.." More details at https://www.reddit.com/r/Thunderbird/comments/1mo693n/comment/n8ammvq/