Email application uses Qt Messaging Framework (QMF) as a backend.
QMF with tracker integration is available at
Detailed QMF documentation is available in /doc subfolder of source package
List of features is available in [Meego Bugzilla]
Discussion of Calendar development happens in the issue tracker, on the [Meego Developer list] and on IRC (freenode.org, #meego-calendar).
Source code can be found on [meego.gitorious.org].