What is the problem?

Most likely your antivirus, that is why we recommend a general exception in antivirus products for the Thunderbird profile folder. However any application that causes contention when Thunderbird tries to save it's settings file can be the culprit. This save occurs when the application shuts down.

You might want to check in your profile folder and see how many copies of the prefs.js file you have. you should only have one, but that that have issues can have hundreds. Neatly saved and numbered as a mute testament to failure.

Exactly which setting name and where are you referring to?

Thanks Matt for the return response, The problem started after a Thunderbird Mail update first of all as this problem has never occurred before in other versions of Thunderbird Mail. That being said, if it is Microsoft Defender then I assume that I would have to go into the firewall or Defender and allow Thunderbird Mail access? I also don't know where in Thunderbird Mail settings is the profile folder? Where would the prefs.js file be located? Is it in MS or Thunderbird? Thanks again for the help, I usually for the most part have little trouble with Thunderbird mail since I started using it more than a decade now.

Matt, I checked the prefs.js file and there is only one so that isn't the problem, and as far as I can tell Microsoft Defender is allowing mail. So I don't know why it is happening but I will just have to go to settings when I open TBM and change the update setting every time. Thanks for the help.

Vin

what is the date on that prefs.js file? Next open Thunderbird and make the change and close it again. Did the date/time change?

Hi Matt, The date is 2/27/25 9:35 am 1 kb, I did as you suggested and the date didn't change.

Thanks, Vin