This would be a handy feature that many people would expect to just
work.
Add support for the user to specify custom headers to be indexed (and
re-index these for existing messages at the next database upgrade).
+Build system
+------------
+Fix to allow a non-source-directory build. For example, the below
+should be made to work:
+
+ mkdir build_dir
+ cd build_dir
+ ../configure
+ make
+
Test suite
----------
Achieve 100% test coverage with the test suite.