Claws Mail for Windows is available as part of the gpg4win package. This port still lacks LDAP, spell checking and an anti-spam plugin.

For antispam, we suggest a filtering rule based on "External program test" with bsfilter.exe, or a filtering proxy like POPFile.

A more recent snapshot than provided by the Gpg4win team is available:
gpg4win-light-1.9.12-svn1044-colin.exe.

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