I recently created a small bundle, JMAPI, to provide support for programmatically opening an email message on Windows platforms using MAPI. Although the bundle’s functionality is restricted to Windows, the bundle is cross-platform. The API is through a single class, jmapi.JMAPI, which supports three methods, one of which queries whether MAPI support is available.
JMAPI was carved from the ruins of the old Java Desktop Interface Components (JDIC) project. With most of JDIC's functionality has was absorbed into Java 6's java.awt.Desktop class, JDIC seems to have died. Not to mention that its binary distributions were wiped out with Oracle's transfer of java.net to Kenai.
The one useful component from JDIC that wasn't absorbed was its attempt to provide cross-platform support for opening mail messages in the user's mail client. Java 6 only supports the mailto: URL scheme. Although mailto: is useful, it is length-limited and, more importantly, doesn't provide for specifying message attachments; some clients provide for an "attachment" field, but its support is uneven.
Unfortunately JDIC's binary distribution is not OSGi-friendly. As my immediate needs were for a way to programmatically open a message using MAPI, I simply ripped out the support from JDIC, and did the minimum to make it work as an OSGi bundle. I didn't have the time to figure out how to rebuild the JNI support libraries (it has references to MFC and ATL), so I simply copied in the Windows DLL from JDIC 0.9.5; unfortunately this is 32-bit only. It may be possible to build using VisualStudio Express 2010 by someone with more Microsoft mojo than me.
Source is available up on github and is licensed under the same terms as JDIC with the LGPL.