Latest stable version is 0.93 Beta 9
You may download the latest beta 9 version of Phoenix Mail from the SourceForge files section.Latest alpha version is 0.93 Alpha 10
Additionally, you may download the latest work in progress version of Phoenix Mail (the Alpha version) from SourceForge (from April 20 2005). Both the executable and sourcecode may be downloaded there.
If you are interested in the sourcecode, you could also use the CVS servers as they contain the latest source. If you want to compile the project yourself, take a look at the Development page.