Do you have any product which can clean up files like CCleaner installed on computer? If yes, do not allow it to have any access to Thunderbird files and folders. This type of product is known for deleting session, password, temp files etc.

Somehow I changed the order of my inbox emails into 'blocks' by the same correspondent, and I want to get them back to a chronological order, either ascending or descending order.

Chisi Your issue has nothing to do with the question, which is about a selected setting not sticking after restarting Thunderbird.

So it would be better to ask your own question.

I don't understand your response. I do not know how to return my email folder to a chronological sequence. I was looking for something and inadvertently changed my email inbox folder to blocks of mail from the same senders. I can't figure out how to get it back to the sequential dates.

It means forum rules are against hijacking another persons thread. Open your own thread and ask your question with details of your issue.

Once again I do not understand what you are talking about. I have a problem, I went to Mozilla for help, I followed the instructions and used the interface, and now I'm being accused of 'hijacking another person's thread' what is that all about?