Rui CarmoCorreo is an alternative e-mail client for Mac OS X that was recently updated for Leopard support (think of it as being Thunderbird ‘s Camino, and you won’t be too far off):
Correo is an alternative e-mail client for Mac OS X that was recently updated for Leopard support (think of it as being Thunderbird ‘s Camino, and you won’t be too far off):