[Exim] exim -HUP

hi,

i have an exim runing wating for incomming connection.
if i kill it to reload it, i suppose i might loose some important mail.

but sometimes (at rare occasion), i need to update some conf,
so you would say : kill -HUP exim_pid so exim never stop runing.
but how about if I have to update macro def, instead of the conf file
itself, i.e: change the value of MACRO_NAME that i have set with exim -DMACRO_NAME

thank you for your help

Edouard