Yes the file format is proprietary. Several export methods are available which provide essentially full access to your data outside of Ultra Recall (specifically csv and xml - which can also be transformed into html).
http://www.kinook.com/blog/?p=18
We do not have plans to implement mail client functionality within Ultra Recall.
Here is a link to our "roadmap" for Ultra Recall:
http://kinook.com/Forum/showthread.php?s=&threadid=993. One note: it has not been updated since the recent release of the 3.0 major version release...