Mozilla Thunderbird is a free open source email client. It is one of the best program with lots of features which makes emaling safer, and better than ever. This is one of my favorite applications created by the Mozilla Foundation.
Recently, the new version of 1.5.0.4 has been released and you could get it from: Mozilla Thunderbird 1.5.0.4. For the full list of new features, please visit: Mozilla Thunderbird 1.5.0.4 release notes.
Kenno's openNOTE 
thanks