Personally i would object strenuously if my unread list updated and the stuff I was working on disappeared as soon as it was marked as read, i.e. as soon as I clicked on the message to read it it would vanish and the reading pane would have nothing in it as I do not use tab to read most mail.

You might find it impractical, I find it essential.

I understand your point, but you are mixing up things.

I'm my case one thing is opening an email, another thing is explicitly setting it as read.

If I am in the main view, filtered with Uread only, and "I" mark an email as Read, it is quite logical that I want it to disappear.

Maybe I have read it through the preview pane and have no need to process it further.

However, it is also true that with my settings opening an email or just moving over it doesn't ever set it automatically as Read, i.e. the only way to have an email marked as read is ti manually set it. That could explain why it's essential for you and impractical for me.

You are more than welcome to suggest an idea about how unread lists work. But this is not the place to do it. See https://connect.mozilla.org/t5/ideas/idb-p/ideas There is also a link on the Thunderbird help menu.

It is essential to me, because I do not get to read the email at all and once the mail disappears from my view it will be in a folder of over 100,000 emails sorted in thread thread and by date. So finding it will be almost impossible without changing sort orders and threading settings and hoping I was quick enough to notice the subject line before I clicked.

For you, you have the inconvenience of having the email stay around for a few minutes.

Thank you so much for the advice @Matt, and forgive my ignorance about it. Have a great day!