Just using Thunderbird with 3 separate accounts, each with about 30 folders, and it occurred to me that Thunderbird should have tabbed email. This would allow me to focus completely on the one account I am using at the moment. The tab could show the number of new emails, etc.
Maybe I am just tired of having too many trees (tree controls, not cellulose-based life forms) in my life. I think this would be a great change for Thunderbird.