Thunderbird does not have a preview anything. There is a reading pane, or a reading tab.

clearly with the first assumption being incorrect, I am having difficulty with the second. I can right click a message and select forward as attachment or Forward as inline. Neither marks the message as read in the original list. Not that I understand why. I would have thought when you forward, inline particularly, that the message has been read, unless you closed your eye while doing the forward.

So I would appreciate if you could provide the exact steps to replicate what you are doing as I simply can not do it. You might also want to restart Thunderbird in Troubleshoot mode and continue when prompted. Is this still occurring? If not you probably have an addon that is causing this non standard behaviour.

Thanks for your quick comments. I'll try your troubleshoot mode suggestion.

The culprit apparently was the Identity Chooser extension. Thanks again, Matt.

I'm on Thunderbird 102.10.0 and both _Inline_ and _Attachment_ are greyed out in the _Forward As_ menu.

I disabled the _Correct Identity_ plugin. But it doesn't change anything. I can only forward inline using the _Forward_ menu option.

PS: Why is proper Markdown syntax no supported in the editor?

After restarting Thunderbird it appears to work again (with Correct Identity plugin enabled). Sorry about the noise.