le psoebr (Forbróir) ar Aib. 5, 2017 · buan-nasc

Hey maniootek, I have been able to replicate your problem. The first result is marked as read because it is displayed in the message pane. If, on the other hand, the message pane is closed, the message won't be marked read. Since I assume you'd like to have your message pane open, I think the best workaround is to include a mark as read delay within your Thunderbird preferences. You can find these preferences under Preferences >> Display >> Advanced >> Reading. I use a delay of 5 seconds. In this way, you have the opportunity to select an unread message prior to your message being marked as read. Thanks for the suggestion though, I may be able to figure out some method of opening and closing the message pane in the future but that won't happen any time soon as I'm currently busy with another project. Hope this helps. - psoebr