The button 
launches the 'Mail printer
scheduler'.
This is a sort of timer which can be starting , pausing and stopping
the printing job of the mail addresses.
On Linux it is possible to choose 2 formats of output.
- Mode Text.
- Mode Postscript.
As for GPE you need to write a small script mps-txt and mps-ps
following the selected mode.
If you use the Postscript mode, calling a2ps is not
needed.
For Windows the GPE printer utilities
are used.
The addresses are printed at the position you will specified in the
parameters menu of the core program.
Each letter you will send to the members will receive the address
printed in a place that should fit the transparent window of the
mailing envelopes.
Printing addresses on sticky labels is for a future release.