How to install and setup a mail notifier that works in fluxbox

[user1]

I have popper installed and setup in ubuntu 12.04 unity and it works 
perfect.

I sometime use fluxbox as an alternative to unity and in order to learn 
to use fluxbox.

Popper do not work in fluxbox.

I have installed mailnag and it is running in fluxbox but it do not 
notify when mail arrive.

I have set it up using /opt/mailnag/mailnag_config

I am using gkrellm as system monitor in fluxbox and know it also can 
notify about mail but I do not know how to set it up neither?