Every few minutes? Like 5? 10?

Sounds like something is playing with your system. Installed any Windows "fix me up" utilities?

Sometimes 5 or 10 minutes, occasionally one minute, sometimes a few hours. It may depend on what else I'm doing on the computer; I'm not sure. I don't know what "Windows 'fix me up' utilities" might be but I have not installed anything that I can think of. I do run Windows Update from time to time.

I had this problem when I was on Win7 and it continued when I changed to Win10 a year or so ago and it has persisted thru a number of versions of Tbird. i finally got fed up and asked the question. I'm presently on v. 78.14.0 and I see that v. 91 is offered. I will update if that will fix this issue but I am loath to do frequent updates because they sometimes disable a feature that I find useful and value highly. When I installed v.78 I lost an add-on that allowed me to edit messages after they had been sent to repair typos or other issues; that is sorely missed (Header Tools).

When I installed v.78 I lost an add-on that allowed me to edit messages after they had been sent to repair typos or other issues; that is sorely missed (Header Tools).

You do realize that the only one to see your edits was you. It changed nothing your recipients saw, that copy had already been sent.

The addon is however available for V78 and 91. https://addons.thunderbird.net/en-US/thunderbird/addon/header-tools-lite/

"You do realize that the only one to see your edits was you. It changed nothing your recipients saw."

Duhhh, I hope I'm not that dumb!! I used to use Header Tools a lot to fix up file copies and sometimes to change my From address by putting the message in Outbox and then editing the address before sending. Anyway, it went away on an update but I got it back a little while ago. It /was/ sorely missed but is now back.

I hope this thread will not be distracted from the columns issue.

I have been watching the disappearing Size column and have not noticed any consistency as to when it disappears unless I view another folder, say switch from the Inbox to the Sent folder. In that instance it hangs in there for a second after I make the switch and then disappears. That is a consistent behavior. I reset it while viewing the Sent folder, then it is gone as soon as I return to my Inbox.

After checking Size in the folder list, at the bottom of the list it asks which folders to apply the change to. It makes no difference what I select there – all subfolders or none – it makes no difference. As soon as I switch to another folder the Size column is gone. I've done that reset probably 3000 times in the last few years, so it is a big deal to get this issue fixed. Someone please help. Thanks!!!!!