Delete a message without opening another message
Thunderbird will normally open the next message if you delete the message that you are reading. This is due to it selecting the next message as a sideffect of deleting the current message. If you don't like this behavior there are several workarounds.
Thunderbird 3 or later
- Install the MailTweaks add-on, enable the "Deletion behavior" tweak, and configure it to do "nothing" after a message is deleted.
These extensions don't support Thunderbird 3.x and appear to use an API call that was removed in 3.0 so even if you disabled version checking (in order to install them) they wouldn't work.
- Install the After Delete add-on. It lets you specify what happens after you delete a message such as selecting the previous, next or no message. You may need to set mail.delete_matches_sort_order true using the config editor. However, it may not work if you're configured a IMAP account to mark a message as deleted (rather than moving it to trash) when deleting a message.
- Install the Unselect Message extension. That will change the behavior of the delete button (and delete key) both in the folder listing, and when reading a message in a window.
- Add the "Delete!" button to your toolbar from the Buttons! extension. Use it to delete the message.
- Don't select the message you want to delete. Instead, right click on the message in the folder listing, and select "delete message" from the context menu. This doesn't work if you are configured to preview messages (you enabled the optional message pane in View -> Layout).