Rated 4 out of 5 stars

I've been using this add-on for quite some time, but I was sick of it not working in newer versions of Thunderbird. So I went in and did some modifications, and made my own version of it. You can get it at https://addons.mozilla.org/en-US/thunderbird/addon/realprevnextbuttons-for-new/. I've tested it on Windows 7 and Ubuntu 11.10 in Thunderbird 9.0 - 10.0.1. The icons may not show up in other versions, but the buttons should still work.