[ale] what open source webmail software do you use?

[lists at sourceillustrated.com (John Wells)]

Guys,

I've done a pretty extensive search, but would like to query the group: 
what open source webmail projects do you use?

I'm a long time happy squirrelmail user, but I have a need to provide a
bit flashier, template-driven site to a particular client.

I've looked at horde, and it looks nice, but I really need one that
supports a folder list somewhere on the main screen with message counts,
like squirrelmail does.  Also, horde tries a bit hard to be all things to
all people, and problems are introduced accordingly.

Heck, if it doesn't provide the folder list, I might consider it anyway
and add it in.  As long as it's template-driven so modifying look and feel
isn't a nightmare (I love squirrelmail, but look and feel is so tightly
wrapped in the code it's difficult to customize).

Also, I'm flexible to implementation....PHP, Perl, Python, Java, etc...

Thanks,
John