I discovered this today - really good app! Supports POP, IMAP, News etc. Stores settings in local directory (see included Readme when installing). Version 2.3.0 was released today!
Win32 zip binary: http://sylpheed.sraoss.jp/sylpheed/win3 ... -win32.zip
Please note: After you unzip, there are a lot of multi-language related files etc which you can safely delete. After these deletions, the install size on disk is ~10MB.