We know that some of you wanted to be able to disable the preview/reading pane because you do not want to open suspicious emails and wanted a way to delete without opening the email. Although there's really no danger in opening any kind of emails, we do understand how to some users this feature is important. That's why Mailbird now support disabling your preview pane. To enable this feature simply click the Mailbird menu located at the top left of your Mailbird window, go to settings>appearance, and disable "show reading pane"
And that's it, you can now open your email by double clicking on it.