I am having the same issue but only with some emails. It looks like it started on 8/7/25. The emails with the issue have either a dash or a blank for the sender, a blank subject, text in the message, and some have code in the message. Emails sent from my iPhone have the issue as well some from a few other senders. I checked "Leave messages on server" in Thunderbird then checked the emails on the server. The emails on the server do not have the issue. I am also running Bitdefender Total Security. Is there any way to tell if the emails with the issue are coming from a POP or IMAP account?

Just cross linking another discussion: Corrupted btinternet emails

Problem went away when I temporarily uninstalled BD, came back when I reinstalled it, I am also running 27.0.53.265 of BD.

I have this same problem, Started 8/11. Have Bitdefender also. Any clues for a solution??

I also use eM Client for another email account. Some testing showed the issue is not occurring in eM Client. I updated Thunderbird yesterday after the issue started and it still existed after the update. This does appear to be be an issue with Bitdefender restrictions for Thunderbird after a recent Bitdefender update. I have not tried any of the fixes posted here, but will do that in a couple of days if no definitive answer has been received from Mozilla support.

here's the response from Mozilla :( I'll try contacting BitDefender tomorrow Manu Andino, Aug 12, 2025, 08:08 CST

Hi there,

Thanks for your email.

Sadly, I'm unable to address your Thunderbird issues; however, please note that I am not trying to deflect your concerns. It is just that we only have the ability to help with issues directly related to Mozilla accounts or some premium services such as Mozilla VPN.

At this time, the best and only place to get advice on Thunderbird issues is the Community Forum. Our community volunteers may be able to provide you with specific guidance on your concern.

Alternatively, you could file a bug in Bugzilla, which is Mozilla's system for tracking defects in Mozilla products such as Thunderbird. You can learn how to file a bug in the article below:

- "_File a bug report or feature request for Mozilla products_"

I apologize that there is not much help that can be provided from our side with Thunderbird issues, but rest assured that if you ever encounter another issue signing into your Mozilla account, that would surely be something that we could help you with.

Have a nice day!

Mozilla Support Team Privacy ∙ Legal

here's the response from Mozilla :( I'll try contacting BitDefender tomorrow Manu Andino, Aug 12, 2025, 08:08 CST Hi there, Thanks for your email. Sadly, I'm unable to address your Thunderbird issues; however, please note that I am not trying to deflect your concerns. It is just that we only have the ability to help with issues directly related to Mozilla accounts or some premium services such as Mozilla VPN. At this time, the best and only place to get advice on Thunderbird issues is the Community Forum. Our community volunteers may be able to provide you with specific guidance on your concern....

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/

@Wayne Mery....help for a comp dummy please :) simply explain what this means "Just click on update in systray and reboot once completed. " I feel so stupid lol

https://www.google.com/search?q=bitdefender+update+tray+or+systray&oq=bitdefender+update+tray+or+systray&gs_lcrp=EgZjaHJvbWUyBggAEEUYOdIBCTExNzEzajBqNKgCALACAQ&sourceid=chrome&ie=UTF-8

bitdefender shows updated 48 mins ago and errors remain the same. went to sys via notification and unablr to right click

bitdefender shows updated 48 mins ago and errors remain the same. went to sys via notification and unablr to right click

In that case, Uninstall BD, download it from their website, and reinstall