All of my emails are being marked as read immediately. I have that option turned off in settings on all devices. I am not using bit defender. This only started after I moved to a windows 11 computer. I only have one account

Marked as read immediately in what way? You select the folder and it is full of read mail? or you select the email and it is immediately marked as read

There is a variety of behavior,

I am just talking here about my inbox.

Behavior one - A new message arrives and instantly changes to read (not bolded) on arrival even if I have not viewed the message.

For instance I signed in to Mozilla to respond to this and I received an alert message that there was a new sign in - this message appeared in my inbox and immediate became marked as read though I had not actually viewed the message or clicked it or anything.

The other behavior - which now seems to be happening after I switched everything to never mark as read - is that messages come in and are marked as unread, and I have to physically change the designation to "Mark as Read" even if click and view the message, it remains as Unread until I do that.

What I would like is the behavior I had on the Windows 10 machine - which was when a new message comes in, it shows as unread until I read it... and then as soon as I read it, it automatically switches to being marked as Read. Which seems like it should be the default behavior.

To continue on this - the two behaviors now shown (either fixed on unread until physically marked to read) or automatically switching to read on arrival, are apparently random. Some messages do one thing and some do the other. I have tested this with emails sent to myself from other accounts, having friends and family send me emails - and most importantly, occurs randomly when my Clients send me emails.

What does not happen is basic email management behavior - appearing as unread until one reads them.

I have used Thunderbird for well over a decade. This is the first time that issue has occurred. I am using the latest version of Thunderbird.