Claws Mail for Windows is available as part of the gpg4win package. This port still lacks LDAP and spell checking.

New: Since svn1133, an antispam plugin based on Bsfilter is provided. You can add the Mark as spam/ham button to your toolbar by going to Configuration/Preferences/Toolbars/Main window and adding it manually (or click "Use default").

A more recent snapshot than provided by the Gpg4win team is available:
gpg4win-light-2.0.2-svn1303-colin.exe.

If you find bugs in Claws Mail, please report them in our Bugzilla, after verifying that it isn't already reported.