Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.

Thanks, but I have no Add-ons, and the theme is the black theme that comes with version 68.1

Thanks, Try it instead of going into automatic denial. And it might be the black theme. really you not helping yourself.

Ok as a test I just installed the 68.1 64bit version of Thunderbird on a test machine, clean install, I setup one account, tried this again, does the same thing, I set it to mark message as read after 30 seconds, I opened the email and I can see in the background that it marked the message as read immediately upon opening. If I uncheck Automatically mark messages as read, it works correctly, they stay unread. It is ignoring this delay option.

Thanks

Well I figured out what is going on, I do not use message preview, this works if you use the message preview pane, it does not work if you have your email open in their own window.

So it is a bug.

David Kelly said

Well I figured out what is going on, I do not use message preview, this works if you use the message preview pane, it does not work if you have your email open in their own window. So it is a bug.

So what bug did you file?