Try Oxygenate Rated 3 out of 5 stars

This theme seems to have been abandoned for some time. Fortunately the more recently released Oxygenate theme -- built on this foundation -- is actively maintained and updated.

This user has a previous review of this add-on.

Great! Rated 5 out of 5 stars

It works, and it looks very good (really integrated look), I like it very much.

milehigh, thanks for the hints, how to install the latest version. I don't know, why they don't update the file here. It's a pity, but I appriciate their work with 5 stars.

It is working in Thunderbird 11 (on Kubuntu 12.04), too, just follow the steps in milehigh's post.

fantastic but doesn't work on WIN7 Rated 4 out of 5 stars

fantastic look. but it doesn't work on WIN7 thunderbird 3.*

Rated 4 out of 5 stars

I am not a huge fan of the Oxygen icons, but all in all this is a very sleek theme. As do some of the others, I miss the menu icons, but could not find any lack or flaw in functionality.

Rated 4 out of 5 stars

Great step towards a KDE4 look.

Rated 5 out of 5 stars

This Addon is essential for anyone who would like to use TB in KDE! But please update it so it works with 3.1...

This review is for a previous version of the add-on (2.0). 

Rated 5 out of 5 stars

Well I took a gamble. It installed in my Thunderbird 3.0.1 in Opensolaris and works. I was hoping it would solve my scroll-bar problem but it didn't. But I figured maybe somebody else may want to try this in Opensolaris so they get my thumbs-up.

This review is for a previous version of the add-on (2.0). 

Rated 5 out of 5 stars

Very nice theme, thanks!

This review is for a previous version of the add-on (2.0). 

Rated 5 out of 5 stars

Looks great. Thanks

This review is for a previous version of the add-on (2.0). 

Rated 5 out of 5 stars

Looks SO much better alongside my other KDE applications -- thank you!

This review is for a previous version of the add-on (2.0). 

Rated 5 out of 5 stars

Looks very nice. Great theme.

This review is for a previous version of the add-on (2.0). 

Rated 4 out of 5 stars

Thanks for this theme, I waas truly waiting for it. It looks fantastic in my kde4!

If I can make some remarks, I'd like to see some more menu icons and at least the two icons for the "spam" and "archive" buttons in the mail header area. I'd also change the icon which appears when you open a mail message: instead of the server icon, you can use a mail icons (something like the "write new" (sorry, my TB is in Italian and I don't remember english label precisely) icon but without the green plus symbol.

It would be great if you can add menu icons for enigmail, too.

This review is for a previous version of the add-on (2.0).