"Spicebird is a cross-platform email and collaboration client
derived from Mozilla Thunderbird. If you are a fan of Thunderbird,
but need more from it than the standard build provides, you may
want to give this new bird a try.
"The latest version, Beta 0.4, was released in January. You can
download it as a tarball for Intel-based Linux or as a binary
installer for Windows. To run the Linux version, all you need to do
is extract the tarball and run the included ./spicebird script from
the command line..."