If it doesn't have to be natively compiled then PyQT would be my first choice. If it has to be compiled to native code then C# + WPF should be good enough. My understanding is that this is just a personal tool, so PyQT should be good enough. If you don't really need a lot of GUI then Python + Tkinter is also pretty good.

Reason for Python: very easy to interact with database and emails. Can put up something useful in under 15 mins and under 15 lines of code.